Some extra money provided for a form of transport (4)
I believe the answer is:
tram
'form of transport' is the definition.
(I know that tram is a type of transport)
'some extra money provided' is the wordplay.
'some' indicates a hidden word (some parts of the word are used).
'TRAM' is hidden within 'extra money provided'.
'for a' acts as a link.
(Other definitions for tram that I've seen before include "Bus on rails" , "Vehicle running on rails in road" , "The Luas, say" , "Take it to the mart" , "Streetcar" .)