Standard-bearer who gaily shows up (4)
I believe the answer is:
iago
'standard-bearer' is the definition.
Both the definition and answer are singular nouns.
Perhaps there's an association between them I don't understand?
'who gaily shows up' is the wordplay.
'shows' indicates the answer is hidden within the clue.
'up' is a reversal indicator (in down clue: letters go upwards).
'ogai' is hidden in the letters of 'who gaily'.
'ogai' in reverse letter order is 'IAGO'.
Can you help me to learn more?
(Other definitions for iago that I've seen before include "Shakespeare's jealous villain" , "stage villain" , "Othello's evil counsellor" , "Othello's treacherous counsellor" , "The villain who tricked Othello" .)