Single bars overlooking river used by comedians (3-6)

'comedians' is the definition.
Although both the answer and definition are plural nouns, I can't see how they can define each other.

'single bars overlooking river used by' is the wordplay.
'single' becomes 'one' (a single thing - only one).
'bars' becomes 'lines' (bar can mean a line).
'overlooking' says to put letters next to each other (in a down clue, some letters go above others).
'river' becomes 'r' (abbreviation for river).
'used by' means one lot of letters goes inside another.
'one'+'lines'='onelines'
'onelines' going around 'r' is 'ONE-LINERS'.

Can you help me to learn more?