Somehow prep former spouse about large puzzle (7)
I believe the answer is:
perplex
'puzzle' is the definition.
(I know that puzzle can be written as perplex)
'somehow prep former spouse about large' is the wordplay.
'somehow' indicates an anagram.
'former spouse' becomes 'ex' (an ex-spouse).
'about' is a charade indicator (letters next to each other).
'large' becomes 'L' (eg in clothes sizes).
'prep' is an anagram of 'perp'.
'ex' put after 'l' is 'lex'.
'perp'+'lex'='PERPLEX'
(Other definitions for perplex that I've seen before include "Nonplus" , "Bewilder" , "Baffle, flummox" , "Mystify" , "Make (someone) baffled" .)