Goal of one entering in the morning (3)
I believe the answer is:
aim
'goal' is the definition.
(aim is a kind of goal)
'one entering in the morning' is the wordplay.
'one' becomes 'i' (Roman numeral).
'entering' is an insertion indicator.
'in the morning' becomes 'am' (AM on a clock).
'i' inserted within 'am' is 'AIM'.
'of' acts as a link.
(Other definitions for aim that I've seen before include "Train" , "Attempt" , "Draw a bead on" , "intent" , "Try to achieve" .)