A particular point in time of some importance (6)
I believe the answer is:
moment
I believe this clue is a triple definition!
'a particular point' is the first definition.
'moment' can be an answer for 'point' (moment is a kind of point). I am unsure of the 'a particular' bit.
'in' is a link.
'time' is the second definition.
(moment is a kind of time)
'of' is a link.
'some importance' is the third definition.
(moment is a kind of importance)
Can you help me to learn more?
(Other definitions for moment that I've seen before include "An exact point of time" , "Occasion" , "Brief second" , "A very brief portion of time" , "tick" .)