Fit men following behind (6)
I believe the answer is:
tailor
'fit' is the definition.
(I've seen this before)
'men following behind' is the wordplay.
'men' becomes 'or' (I've seen this in other clues).
'following' means one lot of letters go next to another.
'behind' becomes 'tail' ('tail' can be a synonym of 'behind'**).
'or' put after 'tail' is 'TAILOR'.
(Other definitions for tailor that I've seen before include "Maker of clothes, men's mostly" , "Specially adapt" , "fitter" , "Fit" , "man of the cloth" .)