Birds - spotted fliers (8)
I believe the answer is:
'birds' is the definition.
(sawbill is a kind of bird)
'spotted fliers' is the wordplay.
'spotted' becomes 'saw' (I've seen this in other clues).
'fliers' becomes 'bills' ('bill' can be a synonym of 'flier').
(Another definition for sawbills that I've seen is " birds".)