Lost boot not seen during football season (4)
I believe the answer is:
fall
'season' is the definition.
(alternative name for autumn)
'lost boot not seen during football' is the wordplay.
I cannot quite see how this works, but
'lost' could be 'l' (abbreviation in sporting league tables) and 'l' is found within the answer.
The remaining letters 'fal' is a valid word which might be clued in a way I don't understand.
This may be the basis of clue (or it may be nonsense).
(Other definitions for fall that I've seen before include "Tumble; autumn" , "Stumble" , "A season in the US" , "Autumn - trip" , "Trip over - flag" .)