Rents out birds (5)
I believe the answer is:
Here is my best explanation:
'birds' is the definition.
(tern is a kind of bird)
'rents out' is the subsidiary indication.
'out' is an anagram indicator.
'rents' with letters rearranged gives 'terns'.
(Other definitions for terns that I've seen before include "Sea bird with long forked tail", "Rents out these birds", "Sea birds with long forked tails", "Seabirds" and "Aquatic birds".)