Punished when discovery is broadcast (5)
I believe the answer is:
fined
'punished' is the definition.
(similar in meaning)
'discovery is broadcast' is the wordplay.
'discovery' becomes 'find' (synonyms).
'is broadcast' indicates a 'sounds like' (homophone) clue (how the word might sound on the radio or TV).
'find' sounds like 'FINED'.
'when' is the link.
(Other definitions for fined that I've seen before include "Imposed financial penalty on" , "Fed in (anag.)" , "Ordered to pay penalty" , "Mulcted" .)