Is left out of hamper? (6)
I believe the answer is:
stifle
'hamper?' is the definition.
(I've seen this in another clue)
'is left out' is the wordplay.
'out' indicates anagramming the letters (out can mean wrong or inaccurate).
'is'+'left'='isleft'
'isleft' anagrammed gives 'STIFLE'.
'of' is the link.
(Other definitions for stifle that I've seen before include "Joint in hind leg of horse" , "Asphyxiate - itself (anag)" , "Quash" , "Curb" , "Smother, suffocate" .)