Joke about king played first cleared the passages (7)

'cleared the passages' is the definition.
The definition and answer can be both to do with communicating as well as being past participle verbs.
Maybe there's a link between them I don't understand?

'joke about king played first' is the wordplay.
'joke' becomes 'gag' (a gag is a joke or witticism).
'about' is an insertion indicator.
'king' becomes 'R' (abbreviation for rex, king in Latin).
'played first' becomes 'led' (I've seen this in another clue).
'gag' going around 'r' is 'garg'.
'garg'+'led'='GARGLED'

Can you help me to learn more?