Groups of musicians I sort out (5)
I believe the answer is:
trios
'groups of musicians' is the definition.
'trios' can be an answer for 'groups' (I have seen 'Groups of three ' mean 'trios' so perhaps 'groups' could also mean 'trios'). I'm not certain of the 'of musicians' bit.
'i sort out' is the wordplay.
'out' indicates an anagram (out can mean wrong or inaccurate).
'i'+'sort'='isort'
'isort' with letters rearranged gives 'TRIOS'.
Can you help me to learn more?
(Other definitions for trios that I've seen before include "Works for three players" , "Groups of three" .)