He may buy rounds and drain bottle after golf (6)
I believe the answer is:
gunman
'he may buy rounds' is the definition.
(rounds as in ammunition)
'drain bottle after golf' is the wordplay.
'drain bottle' becomes 'unman' (unman can mean to deprive of courage or 'bottle').
'after' is a charade indicator (letters next to each other).
'golf' becomes 'g' (phonetic alphabet: alpha, bravo, charlie etc.).
'unman' put after 'g' is 'GUNMAN'.
'and' acts as a link.
(Other definitions for gunman that I've seen before include "Sean O'Casey play 'Shadow of a . . . . . .'" , "Eg, sniper" , "Sean O'Casey wrote 'The Shadow of a . . . . . .'" , "Armed criminal" , "As killer" .)