Sticks it inside in haste (8)
I believe the answer is:
celerity
'haste' is the definition.
(I've seen this before)
'sticks it inside' is the wordplay.
'sticks' becomes 'celery' (I've seen this before).
'inside' means one lot of letters goes inside another.
'celery' going around 'it' is 'CELERITY'.
'in' is the link.
(Other definitions for celerity that I've seen before include "showing a good turn of speed" , "Haste" , "Expedition" , "Quickness" , "Pace" .)