To listen to a thickhead takes courage (5)
I believe the answer is:
heart
'courage' is the definition.
(heart is a kind of courage)
'to listen to a thickhead' is the wordplay.
'to listen to' becomes 'hear' (to hear something is to listen to it).
'a thickhead' becomes 't' (head letter of 'thick').
'hear'+'t'='HEART'
'takes' acts as a link.
(Other definitions for heart that I've seen before include "Earth (anag) -- compassion" , "Kernel" , "bottle" , "Cardiac organ" , "Playing card - pity" .)