Robins, say (5)
I believe the answer is:
birds
'robins say' is the definition.
(robin is a kind of bird)
This is all the clue.
(Other definitions for birds that I've seen before include "Gulls" , "Feathered fliers" , "Egg-laying vertebrates" , "Things may be strictly for them!" , "... strictly receivers of rubbish" .)