Chap managed to collect medal for serving livestock owner (8)
I believe the answer is:
herdsman
'livestock owner' is the definition.
'chap managed to collect medal for serving' is the wordplay.
'chap' becomes 'he'.
'managed' becomes 'ran' (I've seen this before).
'to collect' indicates putting letters inside.
'medal for serving' becomes 'dsm' (distinguished service medal, military award).
'ran' enclosing 'dsm' is 'rdsman'.
'he'+'rdsman'='HERDSMAN'
(Other definitions for herdsman that I've seen before include "Pastoral worker" , "Armed NHS? (anag)" .)