Soldier sent over impressive base (7)
I believe the answer is:
ignoble
'base' is the definition.
('ignoble' can be similar in meaning to 'base')
'soldier sent over impressive' is the wordplay.
'soldier' becomes 'gi' (government issue or general issue).
'sent over' says the letters should be written in reverse.
'impressive' becomes 'noble' ('noble' can be similar in meaning to 'impressive').
'gi' written backwards gives 'ig'.
'ig'+'noble'='IGNOBLE'
(Other definitions for ignoble that I've seen before include "Inferior" , "'Far from the madding crowd's . . . . . . . strife'" , "I belong to base sort" , "degenerate" , "I belong to low sort" .)