Taxonomic group that's found in glasses (7)
I believe the answer is:
species
'taxonomic group' is the definition.
(species is a kind of taxonomic group)
'that's found in glasses' is the wordplay.
'that's' becomes 'ie'.
'found in' indicates putting letters inside.
'glasses' becomes 'specs' ('specs' can be a synonym of 'glasses').
'ie' put inside 'specs' is 'SPECIES'.
(Other definitions for species that I've seen before include "Taxonomic grouping" , "Group of organisms" , "Sort, type" , "Groups of related plants or animals" , "Kind, sort" .)