Instrument features including echo primarily engaged before jam (7,5)
I believe the answer is:
chinese block
'instrument features including echo' is the definition.
I can't judge whether this definition defines the answer.
'primarily engaged before jam' is the wordplay.
'primarily engaged' becomes 'chinese' (I can't explain this - if you can you should believe this answer much more).
'before' means one lot of letters go next to another.
'jam' becomes 'block' (synonyms).
'chinese'+'block'='CHINESE BLOCK'
Can you help me to learn more?
(Another definition for chinese block that I've seen is " percussion instrument".)