Hear about tragic king meeting knight (5)
I believe the answer is:
learn
'hear about' is the definition.
(synonyms)
'tragic king meeting knight' is the wordplay.
'tragic king' becomes 'lear' (I've seen this before).
'meeting' means one lot of letters go next to another.
'knight' becomes 'n' (chess).
'lear'+'n'='LEARN'
(Other definitions for learn that I've seen before include "Succeed in school" , "Study - find out" , "Comprehend" , "Acquire information" , "Hear - memorise" .)