The sad effect when a path gets so untidy (6)
I believe the answer is:
pathos
'the sad effect' is the definition.
The answer and definition can be both related to communication as well as being singular nouns.
Maybe you can see an association between them that I don't see?
'a path gets so untidy' is the wordplay.
'gets' says to put letters next to each other.
'untidy' indicates an anagram.
'so' anagrammed gives 'os'.
'path'+'os'='PATHOS'
'when' acts as a link.
Can you help me to learn more?
(Other definitions for pathos that I've seen before include "Quality inspiring pity" , "Quality of attracting pity" , "Power to excite tender emotion" , "Quality eliciting pity and sympathy" , "Tragic air" .)