Old opponent of Tories now highly content? (4)
I believe the answer is:
whig
'old opponent of tories' is the definition.
(the Whigs were a political party 1678-1859)
'now highly content?' is the wordplay.
'content?' indicates the answer is hidden within the clue (letters contained within the clue).
'WHIG' is hidden within 'now highly'.
(Other definitions for whig that I've seen before include "Old MP" , "Early Liberal" , "Politician such as Walpole" , "Seventeenth century politician" , "British reformist" .)