There's first aid for a girl (7)
I believe the answer is:
theresa
'girl' is the definition.
'there's first aid' is the wordplay.
'first aid' becomes 'a' (1st letter of 'aid').
'theres'+'a'='THERESA'
'for a' is the link.
(Other definitions for theresa that I've seen before include "Woman" , "Girl" , "Maria -, Austr. empress" , "-- May, MP" , "Maria --, Austrian ruler" .)