Birds went quickly in middle of Leicester (6)
I believe the answer is:
cranes
'birds' is the definition.
(crane is a kind of bird)
'went quickly in middle of leicester' is the wordplay.
'went quickly' becomes 'ran' (I've seen this in another clue).
'in' is an insertion indicator.
'middle of' says to take the centre.
The central letters of 'leicester' are 'ces'.
'ran' going within 'ces' is 'CRANES'.
(Other definitions for cranes that I've seen before include "Lifting machines and wading birds" , "Lifting machines or large birds" , "demoiselles" , "Makes an effort to see" , "Lifting machines and long-necked birds" .)