Perhaps cut down rye whiskey after second (3)
I believe the answer is:
Here is my best explanation:
'perhaps cut down rye' is the definition.
'whiskey after second' is the subsidiary indication.
'whiskey' becomes 'w' (alpha bravo charlie delta ...).
'after' means one lot of letters go next to another.
'second' becomes 'mo' (both are short periods of time).
'w' after 'mo' is 'mow'.
(Other definitions for mow that I've seen before include "'Cut, grass say (3)'", "Cut down, usually grass", "Cut (e.g. grass)", "'Cut down, hay, say (3)'", "Scythe", "Cut grass or grain" and "Cut grass on lawn".)