Watson's partner (6)
I believe the answer is:
holmes
'watson's partner' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for holmes that I've seen before include "See 1 down" , "Our 1/4 Across [GOLD MEDALLIST] in 2004" , "Champion solver" , "Conan Doyle's 18" , "Sherlock . . . . . . is a great fictional detective" .)