Agitation from female sitting on knees (4)
I believe the answer is:
flap
'agitation' is the definition.
(I've seen this before)
'female sitting on knees' is the wordplay.
'female' becomes 'f' (abbreviation).
'sitting on' means one lot of letters go next to another.
'knees' becomes 'lap' (I've seen this before).
'f'+'lap'='FLAP'
'from' is the link.
(Other definitions for flap that I've seen before include "Wave up and down - panic" , "Excitement" , "Tab - tizzy - move wings" , "Move wings - panic!" , "Use wings; be agitated" .)