A noted figure, but remiss (3)
I believe the answer is:
lax
'remiss' is the definition.
(I've seen this before)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for lax that I've seen before include "without tension" , "Flabby" , "Slack, not severe" , "Insufficiently strict" , "Careless or slack" .)