Up to a foot less than ever (5)
I believe the answer is:
after
'less than ever' is the definition.
I can't tell whether this defines the answer.
'up to a foot' is the wordplay.
'up' becomes 'ter' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'to' is a charade indicator (letters next to each other) (I've seen this in other clues).
'foot' becomes 'f' (abbreviation).
'a'+'f'='af'
'ter' put after 'af' is 'AFTER'.
Can you help me to learn more?
(Other definitions for after that I've seen before include "Chasing" , "Looking for" , "Following - behind" , "Behind; seeking" , "Following, consequent to" .)