Unsuitable to be a friend to saints? (5)
I believe the answer is:
amiss
'unsuitable' is the definition.
(I've seen this before)
'a friend to saints?' is the wordplay.
'a friend' becomes 'ami' ('friend' in French).
'to saints?' becomes 'ss' (an abbreviation for saint written twice).
'ami'+'ss'='AMISS'
'to be' is the link.
(Other definitions for amiss that I've seen before include "Wrong - awry" , "Revealing fault" , "Badly - wrong" , "astray" , "Haywire" .)