Religious figure tucking into fish — curious problem (9)
I believe the answer is:
conundrum
'problem' is the definition.
(conundrum is a kind of problem)
'religious figure tucking into fish curious' is the wordplay.
'religious figure' becomes 'nun' (I've seen this in another clue).
'tucking into' is an insertion indicator.
'fish' becomes 'cod' (type of fish).
'curious' becomes 'rum' (synonyms).
'nun' inserted into 'cod' is 'conund'.
'conund'+'rum'='CONUNDRUM'
(Other definitions for conundrum that I've seen before include "It's a riddle or a hard question" , "Puzzling problem" , "Puzzle, riddle" , "anagram" , "Difficult question" .)