Fast, but quite the contrary at Le Mans? (4)
I believe the answer is:
lent
'fast' is the definition.
(I've seen this before)
'at le mans?' is the wordplay.
'at' says to put letters next to each other.
'mans?' becomes 'nt' (I can't justify this - if you can you should believe this answer much more).
'le'+'nt' is 'LENT'.
'but quite the contrary' is the link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
(Other definitions for lent that I've seen before include "From Ash Wednesday to Holy Saturday" , "Christian period of abstinence" , "Forty days of fasting" , "Forty days of penance" , "Time of fasting" .)