Shorten short dwarf (3)
I believe the answer is:
doc
'dwarf' is the definition.
(dwarf in Disney's Snow White and the Seven Dwarfs)
'shorten short' is the wordplay.
'shorten' becomes 'dock' (I've seen this before).
'short' means to remove the last letter.
'dock' with its last letter taken off is 'DOC'.
(Other definitions for doc that I've seen before include "Quack" , "Physician (colloq.)" , "scaled-down version of GP" , "Medic (colloq.)" , "Fox perhaps" .)