Het up about part of phrase (3)
I believe the answer is:
the
'part of phrase' is the definition.
I don't know anything about this answer so I cannot tell whether it can be defined by this definition.
'het up' is the wordplay.
'up' is an anagram indicator.
'het' anagrammed gives 'THE'.
'about' acts as a link.
Can you help me to learn more?
(Other definitions for the that I've seen before include "The most frequently occurring word in the Bible (and in this clue!)" , "Last words of story" , "Born - - - - - - - - (carol)" , "Finis" , "Over - - moon" .)