Works progressing slowly in large Greek city (6)
I believe the answer is:
largos
'works progressing slowly' is the definition.
(a largo is a slow musical work)
'large greek city' is the wordplay.
'large' becomes 'L' (eg in clothes sizes).
'greek city' becomes 'argos' (I've seen this in another clue).
'l'+'argos'='LARGOS'
'in' is the link.
(Other definitions for largos that I've seen before include "Slow pieces of music" , "Movements" .)