Nasty slur withdrawn from soul brother playing instrument (7)
I believe the answer is:
theorbo
'playing instrument' is the definition.
'theorbo' can be an answer for 'instrument' (I've seen this before). I am not certain of the 'playing' bit.
'nasty slur withdrawn from soul brother' is the wordplay.
'nasty' indicates an anagram (a nasty or wrong spelling).
'withdrawn from' suggests deleting specific letters.
'soul'+'brother'='soulbrother'
'soulbrother' with 'slur' taken away is 'obother'.
'obother' with letters rearranged gives 'THEORBO'.
Can you help me to learn more?
(Other definitions for theorbo that I've seen before include "old instrument" , "Lute-like instrument; O bother (anag.)" , "... something large to play" , "Antique instrument" , "Old lute with two necks" .)