Displayed debonair boyishness, untoward at heart (2,4)
I believe the answer is:
on show
'displayed debonair boyishness untoward' is the definition.
I don't know anything about this answer so I can't judge whether it can be defined by this definition.
'at heart' is the wordplay.
I cannot really understand how this works, but
'at' could be 'on' (location) and 'on' is located in the answer.
'heart' could be 'h' (card game abbreviation) and 'h' is found in the answer.
The remaining letters 'sow' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for on show that I've seen before include "being demonstrated" , "Exhibited" .)