Plot a feature grasped by couple (9)
I believe the answer is:
machinate
'plot' is the definition.
(I know this)
'a feature grasped by couple' is the wordplay.
'feature' becomes 'chin' (facial feature).
'grasped by' means one lot of letters goes inside another (I've seen this in other clues).
'couple' becomes 'mate' (synonyms).
'a'+'chin'='achin'
'achin' placed into 'mate' is 'MACHINATE'.
(Other definitions for machinate that I've seen before include "concoct a plot" , "Plot to do harm" , "scheme" , "Plan" .)