Discover a little gnu near Thetford (7)
I believe the answer is:
unearth
'discover' is the definition.
(to unearth is to discover or find)
'a little gnu near thetford' is the wordplay.
'a little' says the answer is hidden in the clue (a little bit of the clue).
'UNEARTH' is hidden in the letters of 'gnu near thetford'.
(Other definitions for unearth that I've seen before include "Track down" , "Dig up - uncover" , "Excavate, dig up" , "Expose" , "Find by digging" .)