Pair wandering around Iran having accident by river (8)
I believe the answer is:
riparian
'by river' is the definition.
(riparian means on the banks of a river)
'pair wandering around iran having accident' is the wordplay.
'wandering around' indicates an anagram (I've seen this in other clues).
'having accident' indicates anagramming the letters (an injured form of the letters).
'pair' anagrammed gives 'ripa'.
'iran' with letters rearranged gives 'rian'.
'ripa'+'rian'='RIPARIAN'
(Other definitions for riparian that I've seen before include "near a river" , "living by the river" , "along river bank" , "Relating to river banks" , "Relating to a riverbank - Iran pair (anag)" .)