Girl in love we disconcert (7)
I believe the answer is:
overawe
'disconcert' is the definition.
(thesaurus)
'girl in love we' is the wordplay.
'girl' becomes 'vera' ().
'in' means one lot of letters goes inside another.
'love' becomes 'o' (love means zero in tennis).
'o'+'we'='owe'
'vera' put within 'owe' is 'OVERAWE'.
(Other definitions for overawe that I've seen before include "put off" , "Make weak or helpless with dominating presence" , "Fill with fear and wonder" , "profoundly impress" , "Cow" .)