Understand, and shortly after that become livid (6)
I believe the answer is:
seethe
'become livid' is the definition.
I can't judge whether this definition defines the answer.
'understand and shortly after' is the wordplay.
'understand' becomes 'see' (synonyms).
'and' says to put letters next to each other.
'shortly' means to remove the last letter.
'after' becomes 'then'.
'then' with its final letter removed is 'the'.
'see'+'the'='SEETHE'
'that' acts as a link.
Can you help me to learn more?
(Other definitions for seethe that I've seen before include "Boil; fume with suppressed rage" , "Be silently angry" , "Bubble, almost boil" , "Feel intense rage" , "(Of liquid) boil" .)