Head of Nasa died after instrument exposed to radiation (5)

'exposed to radiation' is the definition.
The definition and answer can be both related to change as well as being past participle verbs.
Perhaps you can see an association between them that I can't see?

'head of nasa died after instrument' is the wordplay.
'head of' says to take the initial letters.
'died' becomes 'd' (abbreviation next to the year of someone's death).
'after' means one lot of letters go next to another.
'instrument' becomes 'uke' (short for ukulele).
The initial letter of 'nasa' is 'n'.
'd' after 'uke' is 'uked'.
'n'+'uked'='NUKED'

Can you help me to learn more?