A very sad outing to catch the right rival (9)
I believe the answer is:
adversary
'rival' is the definition.
(thesaurus)
'a very sad outing to catch the right' is the wordplay.
'outing' indicates anagramming the letters (an outing implies travelling).
'to catch' means one lot of letters goes inside another.
'the right' becomes 'r' (common abbreviation).
'a'+'very'+'sad'='averysad'
'averysad' anagrammed gives 'advesary'.
'advesary' placed around 'r' is 'ADVERSARY'.
(Other definitions for adversary that I've seen before include "Opponent or enemy" , "Antagonist, opponent" , "Enemy or rival" , "Foe, opponent" .)