Impress space commander (6)
I believe the answer is:
emboss
'impress' is the definition.
(I know that emboss is a more specific form of impress)
'space commander' is the wordplay.
'space' becomes 'em' (in typography, a space as wide as a letter 'm').
'commander' becomes 'boss' (I've seen this in another clue).
'em'+'boss'='EMBOSS'
(Other definitions for emboss that I've seen before include "Impress" , "Chase" , "Make a surface design in low relief" , "Make a raised carving" , "Bring about relief" .)