React when the person goes off key (7)
I believe the answer is:
respond
'react when' is the definition.
'respond' can be an answer for 'react' (synonyms). I'm not sure about the 'when' bit.
'person goes off key' is the wordplay.
'goes off' is an anagram indicator.
'key' becomes 'd' (musical key).
'person' anagrammed gives 'respon'.
'respon'+'d'='RESPOND'
'the' acts as a link.
Can you help me to learn more?
(Other definitions for respond that I've seen before include "Reply - react" , "Write back" , "Answer back" , "State in reply" , "Answer or react" .)