Hollow squash on smooth woody plant (5)
I believe the answer is:
shrub
'woody plant' is the definition.
(shrub is a kind of woody plant)
'hollow squash on smooth' is the wordplay.
'hollow' suggests removing the centre.
'on' is a charade indicator (letters next to each other).
'smooth' becomes 'rub' (rub can mean to smooth or sand down).
'squash' with its centre removed is 'sh'.
'sh'+'rub'='SHRUB'
(Other definitions for shrub that I've seen before include "Elder" , "box, say" , "Small woody plant" , "Bushy plant" , "Drink of rum, fruit juice and spices" .)