Insincere talk when philosopher is given a hearing (4)
I believe the answer is:
cant
'insincere talk' is the definition.
(I've seen this before)
'philosopher is given a hearing' is the wordplay.
'philosopher' becomes 'Kant' (Immanuel Kant, 1724-1804).
'is given a hearing' shows a homophone (sound like).
'kant' sounds like 'CANT'.
'when' acts as a link.
(Other definitions for cant that I've seen before include "'Language of a group, Travellers say (4)'" , "Lacks ability" , "Hypocritical talk sounding negative" , "peculiar talk" , "make a lot pay?" .)