Second copper stopping payment for grass (6)
I believe the answer is:
fescue
'for grass' is the definition.
(I've seen this before)
'second copper stopping payment' is the wordplay.
'second' becomes 's' (common abbreviation).
'copper' becomes 'Cu' (chemical symbol).
'stopping' is an insertion indicator (stopping can mean blocking a gap).
'payment' becomes 'fee' (payment for a job).
's'+'cu'='scu'
'scu' placed inside 'fee' is 'FESCUE'.
(Other definitions for fescue that I've seen before include "Pasture grass often found on golf course putting greens" , "Pasture and fodder grass" , "A fine pasture grass" , "Type of pasture grass" , "It might be part of green" .)