Progressive group starts to attract support round city in Texas (2,4)
I believe the answer is:
el paso
'city in texas' is the definition.
(I've seen this in another clue)
'progressive group starts to attract support round' is the wordplay.
'progressive group' becomes 'ELP' (Emerson, Lake and Palmer).
'starts to' suggests taking the first letters.
'round' becomes 'o' (o is a circular letter).
The initial letters of 'attract support' is 'as'.
'elp'+'as'+'o'='EL PASO'
(Other definitions for el paso that I've seen before include "West Texas town" , "City of Texas on the Rio Grande; aslope (anag.)" , "city on Mexican border" , "US city" , "Texan city" .)