Remedy for a dog with a sore tail (4)
I believe the answer is:
cure
'remedy' is the definition.
('cure' can be a synonym of 'remedy')
'a dog with a sore tail' is the wordplay.
'a dog' becomes 'cur' (cur is a kind of dog**).
'with' means one lot of letters go next to another.
'tail' says to take the final letters.
The final letter of 'sore' is 'e'.
'cur'+'e'='CURE'
'for' is the link.
(Other definitions for cure that I've seen before include "Foreign priest" , "Preserve by smoking - make better" , "Restore to health or preserve with salt" , "Make better or preserve in salt" , "priest without an accent" .)