The wind can turn a bit variable (3)
I believe the answer is:
air
'the wind' is the definition.
(air is a kind of wind)
'turn a bit variable' is the wordplay.
'turn' says the letters should be written backwards.
'a bit' says the answer is hidden in the clue (the answer is formed by a bit of the clue).
'ria' is hidden in the letters of 'variable'.
'ria' written backwards gives 'AIR'.
'can' acts as a link.
(Other definitions for air that I've seen before include "The earth's atmosphere" , "a life support" , "- - on a G-string" , "Ventilate with breathing gas" , "Gas mixture required for breathing" .)