Expert in garden centre went quickly (5)
I believe the answer is:
raced
'went quickly' is the definition.
(I've seen this before)
'expert in garden centre' is the wordplay.
'expert' becomes 'ace' (ace can informally mean very good).
'in' means one lot of letters goes inside another.
'centre' means to look at the middle letters.
The middle letters of 'garden' are 'rd'.
'ace' inserted into 'rd' is 'RACED'.
(Other definitions for raced that I've seen before include "Sped" , "Took part in competition of speed" , "Rushed" , "Ran competitively" , "bolted" .)