Football club’s revolutionary succeeded in field (7)
I believe the answer is:
chelsea
'football club's' is the definition.
(Chelsea FC)
'revolutionary succeeded in field' is the wordplay.
'revolutionary' becomes 'Che' (Che Guevara the Marxist revolutionary).
'succeeded' becomes 's' (genealogical abbreviation).
'in' means one lot of letters goes inside another.
'field' becomes 'lea' (lea can mean a meadow or field of grass).
's' inserted within 'lea' is 'lsea'.
'che'+'lsea'='CHELSEA'
(Other definitions for chelsea that I've seen before include "bun offered" , "The Blues of Stamford Bridge" , "Kind of bun that's flat" , "Hillary Clinton's daughter" , "London Blues" .)