Cancel, having to back one talk (9)
I believe the answer is:
negotiate
'talk' is the definition.
The answer and definition can be both to do with communicating as well as being verbs in their base form.
Maybe you can see a link between them that I can't see?
'cancel having to back one' is the wordplay.
'cancel' becomes 'negate' (I've seen this before).
'having' is an insertion indicator.
'back' says the letters should be written in reverse.
'one' becomes 'I' (Roman numeral).
'to' written backwards gives 'ot'.
'ot'+'i'='oti'
'negate' going around 'oti' is 'NEGOTIATE'.
Can you help me to learn more?
(Other definitions for negotiate that I've seen before include "Pass round" , "I get a note (anag) - bargain" , "Discuss the terms of an arrangement" , "Try to reach agreement through discussion" , "as diplomat does" .)