Small insect -- it's amazing for biologists, perhaps (10)
I believe the answer is:
scientists
'biologists perhaps' is the definition.
(biologist is a kind of scientist)
'small insect it's amazing' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'amazing' is an anagram indicator.
'insect'+'its'='insectits'
'insectits' is an anagram of 'cientists'.
's'+'cientists'='SCIENTISTS'
'for' acts as a link.
(Other definitions for scientists that I've seen before include "They study" , "Eg, physicists, biologists" , "Boffins" , "Insects sit (anag.)" .)