Child caught on a Spanish island (7)
I believe the answer is:
minorca
'spanish island' is the definition.
(Minorca is a Spanish island)
'child caught on a' is the wordplay.
'child' becomes 'minor' (synonyms).
'caught' becomes 'c' (cricket abbreviation).
'on' says to put letters next to each other (in a down clue, letters appear on others).
'minor'+'c'+'a'='MINORCA'
(Other definitions for minorca that I've seen before include "Balearic island; O, cram in (anag.)" , "Balearic island (Eng. sp.)" , "Mediterranean island" , "holiday island" , "One of Balearic islands" .)