A hart rising after injury, quite fit (5,2,4)
I believe the answer is:
right as rain
'quite fit' is the definition.
('right as rain' means healthy or fit)
'a hart rising after injury' is the wordplay.
'after injury' indicates an anagram.
'a'+'hart'+'rising'='ahartrising'
'ahartrising' with letters rearranged gives 'RIGHT AS RAIN'.
(Other definitions for right as rain that I've seen before include "In perfect order!" , "Very fine" , "perfectly in order" , "Perfectly fit and well" .)