A pair of Charlies together with Romeo start to annoy doom-monger (9)
I believe the answer is:
cassandra
'a pair' is the definition.
Both the answer and definition are singular nouns.
Perhaps you can see an association between them that I don't see?
'charlies together with romeo start to annoy doom-monger' is the wordplay.
I cannot quite see how this works, but
'with' could be 'and' and 'and' is present in the answer.
'romeo' could be 'r' (phonetic alphabet: alpha, bravo, charlie etc.) and 'r' is present in the answer.
This may be the basis of the clue (or it may be nonsense).
'of' is the link.
Can you help me to learn more?
(Other definitions for cassandra that I've seen before include "Prophetess and Trojan princess" , "Greek prophetess who foretold evil events, but was never believed" , "forecaster" , "was unbelievable" , "One who gave warnings" .)