Tail one wags, extreme part (7)
I believe the answer is:
toenail
'part' is the definition.
(toenail is a kind of part)
'tail one wags extreme' is the wordplay.
'tail one' can be anagrammed to 'TOENAIL'.
Though, I'm not clear how the anagram is indicated.
Can you help me to learn more?
(Other definitions for toenail that I've seen before include "may need this cut?" , "Digital protection!" , "woman in labour" , "Hard plate on part of foot" , "part of leg" .)