Shocking, though seemingly quite proper to a fathead (9)
I believe the answer is:
frightful
'shocking' is the definition.
(thesaurus)
'seemingly quite proper to a fathead' is the wordplay.
I cannot quite see how this works, but
'proper' could be 'rightful' (I've seen this before) and 'rightful' is present in the answer.
'fathead' could be 'f' (head letter of 'fat') and 'f' is located in the answer.
This accounts for all the letters.
This explanation may well be incorrect...
'though' is the link.
Can you help me to learn more?
(Other definitions for frightful that I've seen before include "from hell" , "ugly" , "Appalling" , "very bad" , "horrible" .)