Predilection of monarch supporting large island (6)
I believe the answer is:
liking
'predilection' is the definition.
(thesaurus)
'monarch supporting large island' is the wordplay.
'monarch' becomes 'king' (king is a kind of monarch**).
'supporting' is a charade indicator (letters next to each other) (in a down clue, some letters go below others).
'large' becomes 'l'.
'island' becomes 'i'.
'l'+'i'='li'
'king' after 'li' is 'LIKING'.
'of' acts as a link.
(Other definitions for liking that I've seen before include "Partiality" , "Happy about" , "Penchant" , "Fondness (for thing)" , "weakness" .)