It's in word, English, for insect (7)
I believe the answer is:
termite
'for insect' is the definition.
(termite is a kind of insect)
'it's in word english' is the wordplay.
'in' means one lot of letters goes inside another.
'word' becomes 'term' (term is a kind of word).
'english' becomes 'e' (abbreviation).
'term'+'e'='terme'
'it' put inside 'terme' is 'TERMITE'.
(Other definitions for termite that I've seen before include "White ant" , "Mound builder" , "Ant-like insect that feeds on wood" , "Whitish antlike insect" , "Wood-ant" .)