Try in the morning about one (3)
I believe the answer is:
aim
'try' is the definition.
(thesaurus)
'morning about one' is the wordplay.
'morning' becomes 'am' (as in 12:00 AM).
'about' means one lot of letters goes inside another.
'one' becomes 'I' (Roman numeral).
'am' enclosing 'i' is 'AIM'.
'in the' is the link.
(Other definitions for aim that I've seen before include "mission" , "Purpose in directing the rifle" , "Try to achieve" , "Direct; intention" , "Steady, ... fire" .)