Travel always upset painter (4)
I believe the answer is:
goya
'painter' is the definition.
(thesaurus)
'travel always upset' is the wordplay.
'travel' becomes 'go' ('go' can be a synonym of 'travel').
'always' becomes 'ay'.
'upset' shows that the letters should be reversed in order.
'ay' written backwards gives 'ya'.
'go'+'ya'='GOYA'
(Other definitions for goya that I've seen before include "Span. C18 court painter" , "Old master" , "Francesco de ---, Sp. court painter" , "Great Spanish painter who depicted horrors of war" , "Ay, go to see great Spanish painter" .)