The remedy is, play the number beforehand (7)
I believe the answer is:
nostrum
'the remedy' is the definition.
(nostrum is a kind of remedy)
'play the number beforehand' is the wordplay.
'play' becomes 'strum' (I've seen this before**).
'the number' becomes 'no' (abbreviation for 'number').
'beforehand' says to put letters next to each other.
'strum' after 'no' is 'NOSTRUM'.
'is' is the link.
(Other definitions for nostrum that I've seen before include "Quack remedy or pet scheme" , "Hypothetical remedy for all ills" , "secret potion" , "Patent medicine of highly questionable value" , "Simple, remedy" .)