The extra words in clues gave wordplay leading to {sun, new, inactive, hidden, stranger, radium, Oganessian}, the origins of names of the elements in group 18 of the periodic table, in order of their atomic numbers. Inserting their symbols into down entries would make, respectively: 8 Sa(He)lian, 26 pho(Ne)tic, 6 milit(Ar)ia, 23 ban(Kr)ate, 4 ta(Xe)mes, 2 gu(Rn)ards, 21 gamb(Og)ian. The group number 18 was drawn through the insertion points (any recognisable form of 1 and 8 passing through the right points was accepted). The title referred to 18 as the age of majority and the elements being on the right of the Periodic Table.
Conventions: * = anagram, < = reversal
| No | Extra word | Answer | Explanation |
|---|---|---|---|
| Across | |||
| 1 | every | AGNATE | NAT in AGE |
| 5 | Second | EMERSE | SEAMER * with (Adelaid)E for A(delaide) |
| 10 | part | CURRANT | RAN in CURT |
| 12 | from | ICTAL | TALC * after I |
| 13 | issuing | HA-HA | (SECRET + HA-HA) * = HEARTACHES |
| 14 | mine | MOE | 2 meanings |
| 16 | water | ARUM | A(s) R(eproduction) U(sing) M(onet) |
| 17 | shows | ANIONIC | CONDITIONAL * − TOLD * |
| 18 | invite | TASLET | LATEST * |
| 19 | out | BEAU | BEAT with U (next letter in alphabet) for the last letter |
| 20 | keeping | ASSIGN | AS + SIGN |
| 25 | advanced | SARAPE | S + A + RAPE |
| 27 | Command | RABI | BAR < + I’ |
| 28 | paper | MANIAS | (MAN + AS) around I(gnores) |
| 31 | hotel | YNAMBUS | NAM in BUSY * |
| 33 | nut | NOOP | N + OOP |
| 34 | died | NAE | AE after N |
| 35 | erroneously | DATA | (A TAD) < |
| 36 | inside | ITALA | (SNAG around ITALA) = GALATIANS < |
| 37 | more | SYRPHID | (HAPPY − AP + IS + R(oun)D) * |
| 38 | marked | CEMENT | MEN in CET |
| 39 | orienteer’s | STANCE | ASCENT * |
| Down | |||
| 1 | originally | ACHAR | (K)ARACH(i) * |
| 2 | GUARDS | (A DRUGS) * | |
| 3 | becoming | ARAMAIC | A + DRAMATIC − (ol)D − (agreemen)T |
| 4 | TAMES | STEAM * | |
| 6 | MILITIA | LIMIT * + I + A | |
| 7 | absent | ECHO | (th)E CHO(rus) |
| 8 | SALIAN | ALIA in (S + N) | |
| 9 | fearful | ELOCUTE | ELO + CUTE |
| 11 | Scottish | TENET | TENT around E |
| 15 | institute | ENEMAS | (SAME + ONE − O) < |
| 18 | united | TSUBAS | BUST < + AS |
| 20 | mass | ACRYLIC | UNCRITICALLY * − UNTIL * |
| 21 | GAMBIAN | NAMIBIA * with G for I | |
| 22 | One’s | GRANDPA | PARADING * − I |
| 23 | BANATE | BAN + ATE | |
| 24 | sun | FAUNS | A in FUNS |
| 26 | PHOTIC | H in (OPTIC with P moving up) | |
| 29 | INERT | (FINER + T) − F | |
| 30 | again | SPADE | PAD in SE |
| 32 | Red | MULE | M + ULE |
| Extra | |||
| every Second part from issuing | SUN | (i)S(s)U(i)N(g) | |
| mine water shows | NEW | (mi)NE W(ater) | |
| invite out keeping advanced Command paper | INACTIVE | INVITE * around (A + C) | |
| hotel nut, died erroneously inside | HIDDEN | (H + N (en = nut)) around DIED * | |
| more marked, orienteer’s originally becoming absent | STRANGER | STRONGER with A for O(rienteer’s) | |
| fearful Scottish institute united mass | RADIUM | RAD + I + U + M | |
| One’s sun again Red | OGANESSIAN | (ONE’S + S + AGAIN) * | |