Heading off ladies is over, gents — a sign of things to come (4)
I believe the answer is:
omen
'a sign of things to come' is the definition.
(an omen is a sign of future events)
'heading off ladies' is the wordplay.
'heading off' means to remove the first letter.
'ladies' becomes 'women' (more than one lady).
'women' with its first letter taken away is 'OMEN'.
'is over gents' is the link.
This may not be right. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for omen that I've seen before include "writing on the wall" , "Auspice" , "Warning token" , "Sign of things to come" , "Augur" .)