Suppose this person gets hair cut by American soldier (7)
I believe the answer is:
imagine
'suppose' is the definition.
('imagine' can be a synonym of 'suppose')
'this person gets hair cut by american soldier' is the wordplay.
'this person' becomes 'i'.
'gets' means one lot of letters go next to another.
'hair' becomes 'mane' (I have seen 'Long hair ' mean 'mane' so perhaps 'hair' could also mean 'mane').
'cut by' means one lot of letters goes inside another.
'american soldier' becomes 'gi'.
'mane' enclosing 'gi' is 'magine'.
'i'+'magine'='IMAGINE'
(Other definitions for imagine that I've seen before include "Reckon" , "Fancy - Lennon song" , "Form a mental image in the mind" , "Conjure up in mind,fancy" , "Conceive in the mind" .)