Very fit in woolly (5)
I believe the answer is:
vague
'woolly' is the definition.
(I've seen this before)
'very fit' is the wordplay.
'very' becomes 'v' (abbreviation).
'fit' becomes 'ague' (I've seen this before).
'v'+'ague'='VAGUE'
'in' acts as a link.
(Other definitions for vague that I've seen before include "Indefinite" , "Not clearly expressed, woolly" , "Ill-defined" , "Unclearly defined" , "Uncertain, imprecise" .)