Cool about new bit of intestine (5)
I believe the answer is:
colon
'intestine' is the definition.
(colon is a kind of intestine)
'cool about new bit of' is the wordplay.
'about' indicates an anagram.
'bit of' indicates taking the first letters.
The initial letter of 'new' is 'n'.
'cool' is an anagram of 'colo'.
'colo'+'n'='COLON'
(Other definitions for colon that I've seen before include "cash" , "Panama port; part of intestine" , "almost the end of another" , "that may cut sentence" , "Large intestine; punctuation mark" .)