It's handy when your foot's half dead! (4)
I believe the answer is:
deft
'it's handy' is the definition.
(I've seen this before)
'when your foot's half dead' is the wordplay.
I cannot really see how this works, but
'when' could be 'e' (I've seen this in other clues) and 'e' is found in the answer.
'dead' could be 'd' and 'd' is found in the answer.
'foot' could be 'ft' (synonyms) and 'ft' is present in the answer.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for deft that I've seen before include "Adept" , "Handling things skilfully or neatly" , "Adroit, dexterous" , "Quick and skilful in movement" , "Quick and dexterous" .)