Wonderful agent takes us up (5)
I believe the answer is:
super
'wonderful' is the definition.
(thesaurus)
'agent takes us up' is the wordplay.
'agent' becomes 'rep' (short for representative).
'takes' is a charade indicator (letters next to each other).
'up' says the letters should be written backwards (in down clue: letters go upwards).
'rep'+'us'='repus'
'repus' reversed gives 'SUPER'.
(Other definitions for super that I've seen before include "Incomparable" , "Prefix meaning above or informally great" , "Informally excellent, terrific" , "Prefix meaning terrific or great" , "Informally great, really up there" .)