One feeling for insect in a number trapped by girl (7)
I believe the answer is:
antenna
'one feeling for insect' is the definition.
(an antenna lets an insect feel)
'a number trapped by girl' is the wordplay.
'a number' becomes 'ten' (ten is a number).
'trapped by' means one lot of letters goes inside another.
'girl' becomes 'anna' ().
'ten' going into 'anna' is 'ANTENNA'.
'in' acts as a link.
(Other definitions for antenna that I've seen before include "could send out a message" , "What detects signals" , "connected to 41?" , "Transmitting aerial" , "Aerial - insect feeler" .)