Realise daughter is at Church — remain on outside (7)
I believe the answer is:
discern
'realise' is the definition.
(thesaurus)
'daughter is at church remain on outside' is the wordplay.
'daughter' becomes 'd' (genealogical abbreviation).
'at' says to put letters next to each other.
'church' becomes 'CE' (abbreviation for Church of England).
'on outside' suggests removing the centre (letters on the outside of the word used).
'remain' with its centre taken out is 'rn'.
'd'+'is'+'ce'+'rn'='DISCERN'
(Other definitions for discern that I've seen before include "See" , "Cinders (anag)" , "Perceive - distinguish" , "Make out, distinguish by eye" , "spot" .)