America is gripped by feline affair (7)
I believe the answer is:
liaison
'affair' is the definition.
(I know that affair can be written as liaison)
'america is gripped by feline' is the wordplay.
'america' becomes 'a' (common abbreviation - e.g. in organisation names).
'gripped by' means one lot of letters goes inside another.
'feline' becomes 'lion' (lion is a kind of feline).
'a'+'is'='ais'
'ais' going inside 'lion' is 'LIAISON'.
(Other definitions for liaison that I've seen before include "Cooperation between people or organisations" , "carryon" , "Co-operation; love affair" , "Connection - relationship" , "Intimate relationship" .)