Mastermind tune for worms (8)

I believe the answer is:

planaria

'mastermind tune for worms' is the definition.
I can't tell whether this definition defines the answer.

'mastermind tune' is the wordplay.
'mastermind' becomes 'plan'.
'tune' becomes 'aria' (I've seen this before).
'plan'+'aria'='PLANARIA'

I've seen this clue in The Guardian.

Want a hint initially instead of a full solution? Install my app