Feline treatment for the ache (7)
I believe the answer is:
cheetah
'feline' is the definition.
(I know that cheetah is a type of big cat)
'treatment for the ache' is the wordplay.
'treatment for' indicates anagramming the letters (I've seen this in other clues).
'the'+'ache'='theache'
'theache' with letters rearranged gives 'CHEETAH'.
(Other definitions for cheetah that I've seen before include "Swift-running cat" , "spotted in Africa" , "Long-legged spotted big cat" , "Swift, spotted feline" , "Spotted creature" .)