Decorum shown by party leader, finding smooth lines in speech (2,3,2)
I believe the answer is:
ps and qs
'decorum shown' is the definition.
I know nothing about this answer so I cannot judge whether it can be defined by this definition.
'party leader finding smooth lines in speech' is the wordplay.
'party leader' becomes 'p' (I've seen this in other clues).
'finding' is a charade indicator (letters next to each other).
'smooth' becomes 'sand' (sanding is a kind of smoothing).
'lines' becomes 'queues' (queue is a kind of line).
'in speech' indicates a 'sounds like' (homophone) clue.
'queues' is a homophone of 'qs'.
'p'+'sand'+'qs'='PS AND QS'
'by' is the link.
Can you help me to learn more?
(Other definitions for ps and qs that I've seen before include "Letters" , "Correct social manners" , "one might mind" , "they could need minding" .)