Raise in plain environment, initially (7)
I believe the answer is:
inflate
'raise' is the definition.
(thesaurus)
'in plain environment initially' is the wordplay.
'plain' becomes 'flat' (flat is a kind of plain).
'initially' suggests taking the first letters.
The initial letter of 'environment' is 'e'.
'in'+'flat'+'e'='INFLATE'
(Other definitions for inflate that I've seen before include "Fill with gas" , "Blow or pump up" , "aggrandize them" , "Dilate" , "Puff up" .)