Soft device for fixing shrub (6)
I believe the answer is:
privet
'shrub' is the definition.
(privet is a kind of shrub)
'soft device for fixing' is the wordplay.
'soft' becomes 'p' (musical abbreviation for 'piano').
'device for fixing' becomes 'rivet'.
'p'+'rivet'='PRIVET'
(Other definitions for privet that I've seen before include "hedge material" , "Common hedge shrub" , "Bushy evergreen shrub used for hedges" , "Shrub much used for hedges" , "Hedging shrub" .)