Become visibly cheerful, seeing broadcast plug hit (5,2)
I believe the answer is:
light up
'become visibly cheerful' is the definition.
I can't tell whether this definition defines the answer.
'broadcast plug hit' is the wordplay.
'broadcast' is an anagram indicator.
'plug'+'hit'='plughit'
'plughit' with letters rearranged gives 'LIGHT UP'.
'seeing' acts as a link.
Can you help me to learn more?
(Other definitions for light up that I've seen before include "Become animated" , "Start (a cigarette)" , "suddenly look cheerful" , "cheer!" , "Ignite a cigarette; suddenly show joy" .)