Play with numbers? (7)
I believe the answer is:
musical
'play with numbers' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for musical that I've seen before include "Rent for one" , "Melodious" , "Type of stage show" , "Eg, Cats or Evita" , "Anglo-Saxon tax for protection against invaders" .)