Red can upset routine performer (6)
I believe the answer is:
dancer
'routine performer' is the definition.
'dancer' can be an answer for 'performer' (dancer is a kind of performer). I am unsure of the 'routine' bit.
'red can upset' is the wordplay.
'upset' indicates anagramming the letters.
'red'+'can'='redcan'
'redcan' anagrammed gives 'DANCER'.
Can you help me to learn more?
(Other definitions for dancer that I've seen before include "Ballerina or chorus girl?" , "One moves to music" , "Ballerina cared desperately about Nureyev's lead" , "Nureyev?" , "See 25" .)