Tango and polka will put paid to cosy chat! (6,4)
I believe the answer is:
pillow talk
'cosy chat' is the definition.
(a conversation in bed)
'tango and polka will put paid to' is the wordplay.
'tango' becomes 'T' (phonetic alphabet: alpha, bravo, charlie etc.).
'and' is a charade indicator (letters next to each other).
'put paid to' is an anagram indicator (to put pay to something is to destroy it).
'polka'+'will'='polkawill'
't' after 'polkawill' is 'polkawillt'.
'polkawillt' anagrammed gives 'PILLOW TALK'.
(Other definitions for pillow talk that I've seen before include "Conversation in bed" , "Conversations in bed" , "Bedtime conversation" , "romantic comedy film" .)