If you seek to be a leader, show foresight! (4,5)
I believe the answer is:
look ahead
'foresight' is the definition.
I don't know anything about this answer so I cannot judge whether it can be defined by this definition.
'if you seek to be a leader' is the wordplay.
I cannot quite see how this works, but
'be' could be 'look' (looking is a kind of being) and 'look' is found within the answer.
'a' is found in the answer.
'leader' could be 'head' (head is a kind of leader) and 'head' is found in the answer.
No letters remain.
This explanation may well be incorrect...
'show' is the link.
Can you help me to learn more?
(Another definition for look ahead that I've seen is " Eyes front".)