Roll a constant husband leaves on plate? (7)
I believe the answer is:
spinach
'leaves on plate?' is the definition.
(I've seen this before)
'roll a constant husband' is the wordplay.
'roll' becomes 'spin' (spin is a kind of roll).
'constant' becomes 'c' (mathematical abbreviation).
'husband' becomes 'h'.
'spin'+'a'+'c'+'h'='SPINACH'
(Other definitions for spinach that I've seen before include "Dark green vegetable" , "Vegetable, source of iron" , "Blackboard stand" , "Vegetable leaves" , "Vegetable plant" .)