Understanding things - I recollect (7)
I believe the answer is:
insight
'understanding' is the definition.
(I know that insight is a type of understanding)
'things i recollect' is the wordplay.
'recollect' indicates an anagram.
'things'+'i'='thingsi'
'thingsi' with letters rearranged gives 'INSIGHT'.
(Other definitions for insight that I've seen before include "The ability to perceive the true nature of something" , "Things I have understanding of" , "Intuitive understanding" , "Special knowledge" , "Perceptiveness" .)