Content to thank Fed for word game (7)
I believe the answer is:
hangman
'word game' is the definition.
(I've seen this in another clue)
'content to thank fed' is the wordplay.
'content to' means to look at the middle letters (the contents of the word).
'fed' becomes 'G-man' (both can mean a US federal agent).
The centre of 'thank' is 'han'.
'han'+'gman'='HANGMAN'
'for' acts as a link.
(Other definitions for hangman that I've seen before include "wordgame?" , "Word game - executioner" , "Word-guessing game - executioner" , "Pencil-and-paper game for two" , "Killer" .)