Leader is poorly understood (8)
I believe the answer is:
Here is my best explanation:
'understood' is the definition.
(I've seen this before)
'leader is poorly' is the subsidiary indication.
'poorly' indicates anagramming the letters.
'leaderis' with letters rearranged gives 'realised'.
(Other definitions for realised that I've seen before include "Understood - cashed in", "Became fully aware of or converted into money", "Came to understand", "Came to be aware", "Came to know", "Became aware of in sidereal way", "Sidereal (anag)", "Came to awareness" and "Fully comprehended".)