Behave concerning performance (5)
I believe the answer is:
react
'behave' is the definition.
(thesaurus)
'concerning performance' is the wordplay.
'concerning' becomes 're'.
'performance' becomes 'act' (act is a kind of performance**).
're'+'act'='REACT'
(Other definitions for react that I've seen before include "Behave in response" , "Act as opponent" , "Respond to something" , "Trace (anag)" , "What a chemical might do" .)