Some banana testing is put behind (5)
I believe the answer is:
nates
'behind' is the definition.
(both can mean the buttocks)
'some banana testing is' is the wordplay.
'some' indicates a hidden word (some of the parts of the word are used).
'NATES' is hidden in the letters of 'banana testing is'.
'put' acts as a link.
(Other definitions for nates that I've seen before include "bottom" , "behind" , "Buttocks" .)