Agent gets around centre of Leeds fast (6)
I believe the answer is:
speedy
'fast' is the definition.
('speedy' can be similar in meaning to 'fast')
'agent gets around centre of leeds' is the wordplay.
'agent' becomes 'spy' (spy is a kind of agent).
'gets around' means one lot of letters goes inside another.
'centre of leeds' becomes 'eed'.
'spy' going around 'eed' is 'SPEEDY'.
(Other definitions for speedy that I've seen before include "Express" , "Swift" , "Fast-moving" , "Quick" , "in a hurry" .)