Competitors from London area that is holding blokes back (7)
I believe the answer is:
enemies
'competitors' is the definition.
(enemy is a kind of competitor)
'london area that is holding blokes back' is the wordplay.
'london area' becomes 'se' (abbreviation for South East).
'that is' becomes 'ie' ('i.e.' can be a synonym of 'that is').
'holding' means one lot of letters goes inside another.
'blokes' becomes 'men' (I've seen this in other clues).
'back' is a reversal indicator.
'se'+'ie'='seie'
'seie' enclosing 'men' is 'seimene'.
'seimene' reversed gives 'ENEMIES'.
'from' is the link.
(Other definitions for enemies that I've seen before include "Foes, opponents" , "Foes, hostile groups" , "Foes, adversaries" , "Those we fight" .)