Green mask and whip (7)
I believe the answer is:
rawhide
'whip' is the definition.
(I've seen this before)
'green mask' is the wordplay.
'green' becomes 'raw' (synonyms).
'mask' becomes 'hide' (I've seen this before).
'raw'+'hide'='RAWHIDE'
'and' is the link.
(Other definitions for rawhide that I've seen before include "Untanned animal skin cut to make whips and ropes" , "Whip" , "Stiff untanned leather" , "Leather before tanning" .)