Wart on the foot (7)
I believe the answer is:
verruca
'wart on the foot' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for verruca that I've seen before include "Kind of wart of foot" , "Wartlike growth often on foot" , "Wart on the sole of the foot" , "1 across" , "Viral wart" .)