Plant personnel tucking into sandwich (5)
I believe the answer is:
shrub
'plant' is the definition.
(type of plant)
'personnel tucking into sandwich' is the wordplay.
'personnel' becomes 'HR' (Human Resources).
'tucking into' indicates putting letters inside.
'sandwich' becomes 'sub' (sub is a kind of sandwich).
'hr' inserted into 'sub' is 'SHRUB'.
(Other definitions for shrub that I've seen before include "Woody plant, bush" , "Bushy plant" , "Rose, perhaps" , "Small woody plant" , "Hazel perhaps" .)