March off, insulting PR campaign (5,9)
I believe the answer is:
charm offensive
'pr campaign' is the definition.
'charm offensive' can be an answer for 'campaign' (I have seen 'smarmy campaign' mean 'charm offensive' so perhaps 'campaign' could also mean 'charm offensive'). I'm not sure about the 'pr' bit.
'march off insulting' is the wordplay.
'off' indicates anagramming the letters.
'insulting' becomes 'offensive' (similar in meaning).
'march' anagrammed gives 'charm'.
'charm'+'offensive'='CHARM OFFENSIVE'
Can you help me to learn more?
(Other definitions for charm offensive that I've seen before include "smarmy campaign" , "PR campaign needed" , "Campaign to gain support and become more popular" , "Ingratiating campaign is needed" .)