Cutting constant cuts in assistance (4)
I believe the answer is:
acid
'cutting constant' is the definition.
'acid' can be an answer for 'cutting' (I've seen this in another clue). I am not sure about the 'constant' bit.
'cuts in assistance' is the wordplay.
'cuts' becomes 'c' (this could be a standard abbreviation of which I'm unaware).
'in' indicates putting letters inside.
'assistance' becomes 'aid' (synonyms).
'c' going within 'aid' is 'ACID'.
Can you help me to learn more?
(Other definitions for acid that I've seen before include "something sharp" , "Bitter - drug" , "Polluted precipitation" , "Bitter; biting" , "Sour - LSD" .)