Bird seen round loch is quail (6)
I believe the answer is:
flinch
'is quail' is the definition.
(both can mean to show fear)
'bird seen round loch' is the wordplay.
'bird' becomes 'finch' (finch is a kind of bird).
'seen round' is an insertion indicator.
'loch' becomes 'l'.
'finch' placed around 'l' is 'FLINCH'.
(Other definitions for flinch that I've seen before include "Move quickly as reaction to potential pain" , "Cringe" , "Shrink back with fear" , "Draw back in shock" , "Shrink back or wince" .)