Lass finally catching game, unaccompanied male (4)
I believe the answer is:
Here is my best explanation:
'unaccompanied male' is the definition.
(man attending a social event without a woman)
'lass finally catching game' is the subsidiary indication.
'finally' says to take the final letters.
'catching' is a charade indicator (letters next to each other).
'game' becomes 'tag' (tag is a kind of game**).
The last letter of 'lass' is 's'.
(Other definitions for stag that I've seen before include "speculator wanting quick profit", "one may get in a rut", "Adult male deer, often with antlers", "Stock market speculator", "Game - speculator", "Male deer; speculator", "Without women", "Animal - for men only", "Deer; with only men" and "For men only".)