Little Tom's digit (5)
I believe the answer is:
thumb
I believe this clue is a double definition.
'little tom's' is the first definition.
(tiny folklore character Tom Thumb)
'digit' is the second definition.
(thumb is a kind of digit)
(Other definitions for thumb that I've seen before include "Try to get a lift" , "Hitch (a lift)" , "Opposable digit" , "Pollex, in humans" , "Indicate need for lift" .)