Pledge to collect one, finding lift quickly (5)
I believe the answer is:
hoick
'lift quickly' is the definition.
(to hoick something is to lift it quickly)
'pledge to collect one' is the wordplay.
'pledge' becomes 'hock' (hock can mean to leave with a pawnbroker).
'to collect' indicates putting letters inside (inserted letters are collected by others).
'one' becomes 'i' (Roman numeral).
'hock' enclosing 'i' is 'HOICK'.
'finding' acts as a link.
(Other definitions for hoick that I've seen before include "Pull suddenly" , "Rise up" , "jerk" , "Pull abruptly" , "Lift abruptly" .)