Fester right away in joint (5)
I believe the answer is:
ankle
'joint' is the definition.
(ankle is a kind of joint)
'fester right away' is the wordplay.
'fester' becomes 'rankle' (I've seen this before).
'right' becomes 'r' (common abbreviation).
'away' suggests deleting specific letters.
'rankle' with 'r' removed is 'ANKLE'.
'in' is the link.
(Other definitions for ankle that I've seen before include "Major foot joint" , "Lower leg joint" , "Human joint" , "Location of the talus" , "Joint between foot and leg" .)