Youngsters have caught the wrong bus (4)
I believe the answer is:
'youngsters' is the definition.
The answer and definition can be both people as well as being plural nouns.
Perhaps they are linked in a way I don't understand?
'caught the wrong bus' is the wordplay.
'caught' becomes 'c' (cricket abbreviation).
'the wrong' indicates anagramming the letters.
'bus' is an anagram of 'ubs'.
'have' acts as a link.
Can you help me to learn more?
(Other definitions for cubs that I've seen before include "Young of certain animals" , "Little foxes" , "Young and inexperienced reporters" , "Junior Scouts" , "Young bears" .)