Watch Roman poet run off? (5)
I believe the answer is:
vigil
'watch' is the definition.
(to keep vigil is to keep watch)
'roman poet run off?' is the wordplay.
'roman poet' becomes 'virgil'.
'run' becomes 'r' (cricket abbreviation).
'off?' is a deletion indicator (some letters taken off).
'virgil' with 'r' taken away is 'VIGIL'.
(Other definitions for vigil that I've seen before include "Watchful night" , "Purposeful surveillance to guard or observe" , "Staying awake to keep watch or pray" , "A period of staying awake as for prayer" , "Night-time watch" .)