Insects? They're regularly found by little children (8)
I believe the answer is:
termites
'insects?' is the definition.
(termite is a kind of insect)
'they're regularly found by little children' is the wordplay.
'regularly' means one should take alternating letters (regularly take one letter, leave next etc.).
'found by' means one lot of letters go next to another.
'little children' becomes 'mites' (I've seen this before).
The alternate letters of 'theyre' are 'ter'.
'ter'+'mites'='TERMITES'
(Other definitions for termites that I've seen before include "Flightless insects living in mounds" , "Destructive workers" , "Ant-like social insect that feeds on wood" , "Ant-like insects that feed on wood" .)