Tom's hand tool? (4-3)
I believe the answer is:
cats-paw
'tool?' is the definition.
(both can mean a person used by another)
'tom's hand' is the wordplay.
'tom's' becomes 'cat's' (a tom is a male cat).
'hand' becomes 'paw' (synonyms).
'cats'+'paw'='CATS-PAW'
(Other definitions for cats-paw that I've seen before include "Person used by another for an unpleasant purpose" , "Dupe - nautical hitch - ripples on water in light wind" , "Someone used by another" , "Person used by another to gain an end" , "Person used by another for dangerous business" .)