Suppress issue about sex (3,2)
I believe the answer is:
Here is my best explanation:
'suppress' is the definition.
'issue about sex' is the subsidiary indication.
'issue' becomes 'son'.
'about' means one lot of letters goes inside another.
'sex' becomes 'it' (a common euphemism).
'son' going around 'it' is 'siton'.
(Other definitions for sit on that I've seen before include "Delay dealing with", "Suppress", "Fail to deal with" and "Use as chair; fail to progress (file)".)