Coach returning to pick up personnel in plant (5)
I believe the answer is:
shrub
'plant' is the definition.
(type of plant)
'coach returning to pick up personnel' is the wordplay.
'coach' becomes 'bus' (synonyms).
'returning' says the letters should be written in reverse.
'to pick up' is an insertion indicator.
'personnel' becomes 'HR' (Human Resources).
'bus' in reverse letter order is 'sub'.
'sub' placed around 'hr' is 'SHRUB'.
'in' is the link.
(Other definitions for shrub that I've seen before include "Elder" , "Small woody plant" , "Woody plant smaller than a tree" , "Perhaps Heather" , "Small woody tree" .)