Small shoe that's full of holes (8)
I believe the answer is:
strainer
'that's full of holes' is the definition.
(kitchen implement full of holes)
'small shoe' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'shoe' becomes 'trainer' (I've seen this before).
's'+'trainer'='STRAINER'
(Other definitions for strainer that I've seen before include "Filtering device" , "It separates liquids from solids for trainers" , "to collect leaves?" , "Tea leaf catcher" , "one won't let everything go through" .)