Fly with squadron leader, stop coming in low (8)
I believe the answer is:
mosquito
'fly' is the definition.
(I've seen this before)
'squadron leader stop coming in low' is the wordplay.
'leader' indicates taking the first letters.
'stop' becomes 'quit' ('quit' can be a synonym of 'stop'**).
'coming in' is an insertion indicator.
'low' becomes 'moo' ('moo' can be a synonym of 'low').
The initial letter of 'squadron' is 's'.
's'+'quit'='squit'
'squit' going into 'moo' is 'MOSQUITO'.
'with' is the link.
(Other definitions for mosquito that I've seen before include "British WWII multi-role combat aircraft" , "Insect, the female of which sucks blood" , "Disease-bearing insect" , "Disease-bearing fly" , "Malaria transmitter" .)