Cricket, for example, is popular before school (6)
I believe the answer is:
insect
'cricket for example' is the definition.
(cricket is an example)
'popular before school' is the wordplay.
'popular' becomes 'in' ('in' can mean trendy).
'before' is a charade indicator (letters next to each other).
'school' becomes 'sect' (I've seen this in other clues).
'in'+'sect'='INSECT'
'is' is the link.
(Other definitions for insect that I've seen before include "Creepy-crawly" , "Little creature" , "Ladybird, for example" , "Member of the largest class of creatures" , "Bug" .)