Head of household turned aghast seeing this on X (formerly Twitter) (7)
I believe the answer is:
hashtag
'this on x formerly twitter' is the definition.
I don't know anything about this answer so I cannot judge whether it can be defined by this definition.
'head of household turned aghast' is the wordplay.
'head of' suggests taking the first letters.
'turned' indicates an anagram.
The first letter of 'household' is 'h'.
'aghast' is an anagram of 'ashtag'.
'h'+'ashtag'='HASHTAG'
'seeing' is the link.
Can you help me to learn more?
(Other definitions for hashtag that I've seen before include "Twitter mark" , "Octothorp" , "Word or phrase to aid online searches - hag's hat (anag)" , "component of tweet" , "Number symbol" .)