Variable rents for fliers (5)
I believe the answer is:
terns
'fliers' is the definition.
(tern is a kind of bird)
'variable rents' is the wordplay.
'variable' is an anagram indicator (a varied form of the letters).
'rents' with letters rearranged gives 'TERNS'.
'for' is the link.
(Other definitions for terns that I've seen before include "Aquatic birds" , "Rents out these birds" , "Seabirds" , "Sea bird with long forked tail" , "Sea birds with long forked tails" .)