Saint speaks: has trouble doing so? (8)
I believe the answer is:
stutters
'has trouble doing so?' is the definition.
I can't judge whether this defines the answer.
'saint speaks' is the wordplay.
'saint' becomes 'st' (abbreviation).
'speaks' becomes 'utters' ('utter' can be a synonym of 'speak').
'st'+'utters'='STUTTERS'
(Other definitions for stutters that I've seen before include "Speaks haltingly" , "falters" , "impediments" , "Speaks with hesitant repetition of first consonants" , "Stammers in repeating the first consonants of words" .)