Tease a thick-headed relative (5)
I believe the answer is:
taunt
'tease' is the definition.
(I know that tease can be written as taunt)
'a thick-headed relative' is the wordplay.
'a thick-headed' becomes 't' (this might be a standard abbreviation I've not previously seen).
'relative' becomes 'aunt' (aunt is a type of relative).
't'+'aunt'='TAUNT'
Can you help me to learn more?
(Other definitions for taunt that I've seen before include "Thing said to anger or wound" , "Wounding jibe" , "Mocking remark" , "Gibe" , "Rag, goad" .)