Queen in European country upset Reagan, perhaps (7)
I believe the answer is:
eleanor
'queen' is the definition.
(I've seen this before)
'european country upset reagan perhaps' is the wordplay.
'european' becomes 'E' (abbreviation e.g. EU).
'country' becomes 'lea' (I've seen this before).
'upset' is a reversal indicator.
'reagan perhaps' becomes 'ron' (Ronald Reagan).
'ron' backwards is 'nor'.
'e'+'lea'+'nor'='ELEANOR'
'in' is the link.
(Other definitions for eleanor that I've seen before include "A reel by Ringo (anag) -- Beatles song" , "Female" , "Franklin D. Roosevelt's wife" , "Wife of F. D. Roosevelt" , "Miss Rigby" .)