Silly answer meeting sanctimonious silence (5)
I believe the answer is:
apish
'silly' is the definition.
(I've seen this in another clue)
'answer meeting sanctimonious silence' is the wordplay.
'answer' becomes 'a' (abbreviation eg in Q and A).
'meeting' means one lot of letters go next to another.
'sanctimonious' becomes 'pi' (old-fashioned term for pious).
'silence' becomes 'sh' ('sh' is said to tell someone to be silent).
'a'+'pi'+'sh'='APISH'
(Other definitions for apish that I've seen before include "Silly" , "Foppish" , "Foolish; simian" , "Stupid" , "Foolish; like a monkey" .)