Cook up a disparaging term for MPs (4)
I believe the answer is:
wets
'a disparaging term for mps' is the definition.
I can't judge whether this definition defines the answer.
'cook up' is the wordplay.
'cook' becomes 'stew' (stewing is a kind of cooking).
'up' says the letters should be written backwards (in down clue: letters go upwards).
'stew' in reverse letter order is 'WETS'.
Can you help me to learn more?
(Other definitions for wets that I've seen before include "Moistens" , "Applies moisture" .)