Give life to soldiers in space before (8)
I believe the answer is:
energise
'give life to' is the definition.
('give life to'->'energize' is in my internal thesaurus and 'ize'->'ise')
'soldiers in space before' is the wordplay.
'soldiers' becomes 'gis' (I've seen this in other clues**).
'in' means one lot of letters goes inside another.
'space' becomes 'en'.
'before' becomes 'ere' (usually literary).
'en'+'ere'='enere'
'gis' inserted into 'enere' is 'ENERGISE'.
(Other definitions for energise that I've seen before include "Stimulate activity" , "Give power to" , "Give vitality to" , "give vigour" , "Motivate" .)