Studies concerning marketing tools (5)
I believe the answer is:
reads
'studies' is the definition.
(I know this)
'concerning marketing tools' is the wordplay.
'concerning' becomes 're' (both can mean on a particular topic).
'marketing tools' becomes 'ads' (I've seen this in another clue).
're'+'ads'='READS'
(Other definitions for reads that I've seen before include "Studies (at university)" , "Looks at and undertsands the written word" , "Understands written language" , "Peruses" , "Scans" .)