Stick notice on present (6)
I believe the answer is:
adhere
'stick' is the definition.
(to adhere to something is to stick to it)
'notice on present' is the wordplay.
'notice' becomes 'ad' (short for advert).
'on' means one lot of letters go next to another (in a down clue, letters appear on others).
'present' becomes 'here' (both can mean in attendance).
'ad'+'here'='ADHERE'
(Other definitions for adhere that I've seen before include "Stick with header" , "Remain attached" , "Stick L" , "Stick or cleave to" , "Stick firmly" .)