I can't mess about with word meanings (9)
I believe the answer is:
semantics
'word meanings' is the definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.
'i can't mess about' is the wordplay.
'about' indicates anagramming the letters.
'i'+'cant'+'mess'='icantmess'
'icantmess' is an anagram of 'SEMANTICS'.
'with' is the link.
Can you help me to learn more?
(Other definitions for semantics that I've seen before include "Branch of linguistics to do with meaning" , "Branch of linguistics concerned with meanings" , "The meaning attached to words" , "The significance of a text" , "Meaning to study" .)