In the morning one has a purpose (3)
I believe the answer is:
aim
'a purpose' is the definition.
(synonyms)
'in the morning one' is the wordplay.
'in the' indicates putting letters inside.
'morning' becomes 'am'.
'one' becomes 'i' (Roman numeral).
'am' enclosing 'i' is 'AIM'.
'has' acts as a link.
(Other definitions for aim that I've seen before include "Set sights on, target or goal" , "Point or direct, a weapon say" , "Goal, object" , "anticipated" , "Attempt" .)