A subtle difference in answer welcomed by Sister Clare (6)
I believe the answer is:
nuance
'a subtle difference' is the definition.
(I've seen this in another clue)
'answer welcomed by sister clare' is the wordplay.
'answer' becomes 'a' (abbreviation eg in Q and A).
'welcomed by' is an insertion indicator (letters welcomed inside).
'sister' becomes 'nun' (sister is a term of address for a nun).
'clare' becomes 'ce' (I've seen this in other clues).
'a' inserted into 'nun' is 'nuan'.
'nuan'+'ce'='NUANCE'
'in' acts as a link.
(Other definitions for nuance that I've seen before include "Fine shade of meaning" , "Cue Ann into slight shade" , "Subtle shade of meaning" , "Subtle difference of meaning" , "Subtle variation, in meaning say" .)