A number, after try, cheer (7)
I believe the answer is:
hearten
'cheer' is the definition.
('hearten' can be a synonym of 'cheer')
'a number after try' is the wordplay.
'a number' becomes 'ten' (ten is a kind of number).
'after' says to put letters next to each other.
'try' becomes 'hear' (as in to try someone in court or hear their case**).
'ten' put after 'hear' is 'HEARTEN'.
(Other definitions for hearten that I've seen before include "Buoy" , "Inspire anew" , "Be encouraged" , "Comfort" , "Encourage or cheer in cardiac manner" .)