Retired couple beset by ruminants on the way back (8)
I believe the answer is:
repaired
'retired' is the definition.
(I've seen this before)
'couple beset by ruminants on the way back' is the wordplay.
'couple' becomes 'pair' (synonyms).
'beset by' indicates putting letters inside ('beset' could historically mean 'cover').
'ruminants' becomes 'deer' (deer are a type of ruminant).
'on the way back' shows that the letters should be reversed in order.
'deer' written backwards gives 'reed'.
'pair' inserted inside 'reed' is 'REPAIRED'.
(Other definitions for repaired that I've seen before include "Mended, restored" , "Retired" , "Fixed" , "Restored to good condition" , "Put right - went" .)