Of little importance (5)
'of little importance' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for trivial that I've seen before include "Petty, piffling" , "Insignificant" , "Of little value" , "Piddling" , "Rinky-dink" .)
'of little importance' is the definition.
(minor can mean unimportant)
This is all the clue.
(Other definitions for minor that I've seen before include "Young person below voting age" , "Morris car; tending to melancholy (mus.)" , "One not yet of legal age" , "Of little significance" , "Unimportant or unable to vote" .)