Remedy in pot very good one (7)
I believe the answer is:
panacea
'remedy' is the definition.
(I know that panacea is a type of remedy)
'pot very good one' is the wordplay.
'pot' becomes 'pan' (I've seen this in other clues).
'very good' becomes 'ace' (I've seen this before).
'one' becomes 'a' (a thing is one thing).
'pan'+'ace'+'a'='PANACEA'
'in' is the link.
(Other definitions for panacea that I've seen before include "A cure for everything" , "Cure for all ills" , "Universal medicine" , "that can make anything better" , "Panpharmacon" .)