Huge people in rebuilt semi (7)
I believe the answer is:
'huge' is the definition.
(I know that huge can be written as immense)
'people in rebuilt semi' is the wordplay.
'people' becomes 'men' (men are people).
'in' is an insertion indicator.
'rebuilt' indicates an anagram.
'semi' anagrammed gives 'imse'.
'men' going within 'imse' is 'IMMENSE'.
(Other definitions for immense that I've seen before include "Huge, vast" , "Very big, really huge" , "Unusually great in size" , "Unusually large or great" , "Huge, very big indeed" .)