Put briefly into boiling water, cutting out new cold tripe (4)
I believe the answer is:
blah
'out new cold tripe' is the definition.
'blah' can be an answer for 'tripe' (both can mean nonsense). I'm not certain of the 'out new cold' bit.
'put briefly into boiling water cutting' is the wordplay.
'put' becomes 'lay' (as in laying or putting something down).
'briefly' means to remove the last letter.
'into' indicates putting letters inside.
'boiling water cutting' becomes 'bh' (I can't explain this - if you can you should believe this answer much more).
'lay' with its final letter taken away is 'la'.
'la' placed within 'bh' is 'BLAH'.
Can you help me to learn more?
(Other definitions for blah that I've seen before include "Pretentious nonsense" , "Insipid" , "Pretentious waffle" , "Claptrap" , "bunkum!" .)