Bug trendy splinter group (6)
I believe the answer is:
insect
'bug' is the definition.
(bug can mean an insect)
'trendy splinter group' is the wordplay.
'trendy' becomes 'in' ('in' can mean fashionable).
'splinter group' becomes 'sect' (I've seen this before).
'in'+'sect'='INSECT'
(Other definitions for insect that I've seen before include "Eg, beetle or bee" , "Little creature" , "Bee or beetle, for example" , "Soldier perhaps" , "E.g. cricket" .)