Dwarf cod turned up (3)
I believe the answer is:
doc
'dwarf' is the definition.
(one of the seven)
'cod turned up' is the wordplay.
'turned up' says the letters should be written in reverse.
'cod' reversed gives 'DOC'.
(Other definitions for doc that I've seen before include "scaled-down version of GP" , "One of the seven dwarfs" , "bones" , "Holliday (in 17 24)" , "Main dish" .)