Coach and hot English bodyguard will have an affair (8)
I believe the answer is:
business
'an affair' is the definition.
(thesaurus)
'coach and hot english bodyguard' is the wordplay.
'coach' becomes 'bus' (synonyms).
'and' means one lot of letters go next to another.
'hot' becomes 'in' (both can mean fashionable).
'english' becomes 'E' (abbreviation as in OED).
'bodyguard' becomes 'SS' (the SS was originally Hitler's personal bodyguard).
'bus'+'in'+'e'+'ss'='BUSINESS'
'will have' acts as a link.
(Other definitions for business that I've seen before include "Baby" , "Occupation; trade" , "Firm" , "complicated problem" , "Commerce, trade" .)