Claim papers concealing government department’s U-turn (7)
I believe the answer is:
profess
'claim' is the definition.
(professing is a kind of claiming)
'papers concealing government department's u-turn' is the wordplay.
'papers' becomes 'press' (the newspaper industry).
'concealing' means one lot of letters goes inside another.
'government department' becomes 'FO' (short for Foreign Office).
'u-turn' says the letters should be written in reverse.
'fo' back-to-front is 'of'.
'press' placed around 'of' is 'PROFESS'.
(Other definitions for profess that I've seen before include "State insincerely" , "Affirm faith in (religion)" , "Make open declaration of" , "Claim or declare" , "Declare openly" .)