Veteran's antique clock (3-5)
I believe the answer is:
old-timer
'veteran's' is the definition.
(I've seen this before)
'antique clock' is the wordplay.
'antique' becomes 'old' (similar in meaning).
'clock' becomes 'timer' (something which times).
'old'+'timer'='OLD-TIMER'
(Other definitions for old-timer that I've seen before include "Man of long experience" , "Veteran, elderly person" , "Very long-serving person" , "Male with long experience, maybe a prospector" .)