Lay down before writer (9)
I believe the answer is:
prescribe
'lay down' is the definition.
(thesaurus)
'before writer' is the wordplay.
'before' becomes 'pre'.
'writer' becomes 'scribe' (scribe is a kind of writer**).
'pre'+'scribe'='PRESCRIBE'
(Other definitions for prescribe that I've seen before include "Lay" , "as doctor may order" , "Advise use of (medicine)" , "Order use of (medicine or other treatment)" , "Recommend as beneficial" .)