Rivals hop upon tents and chiefs flee (9)
I believe the answer is:
opponents
'rivals' is the definition.
(opponent is a kind of rival)
'hop upon tents and chiefs flee' is the wordplay.
I cannot quite see how this works, but
'upon' could be 'on' (I've seen this in other clues) and 'on' is found within the answer.
'and' could be 'n' (common abbreviation for 'and') and 'n' is present in the answer.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for opponents that I've seen before include "matches" , "The other side" .)