Concentrate, reading catalogue in French (6)
I believe the answer is:
listen
'concentrate' is the definition.
(I know that listen is a more specific form of the action concentrate)
'catalogue in french' is the wordplay.
'catalogue' becomes 'list' (a catalogue is a list of items).
'in french' becomes 'en' ('in' in French).
'list'+'en'='LISTEN'
'reading' acts as a link.
(Other definitions for listen that I've seen before include "Lend an ear (6)" , "Harken" , "16 (anag.)" , "Give ear (to)" , "Take heed -- 13 (anag)" .)