Paleness from friend left in front of soldiers (6)
I believe the answer is:
pallor
'paleness' is the definition.
('pallor' can be a synonym of 'paleness')
'friend left in front of soldiers' is the wordplay.
'friend' becomes 'pal' (pal is a kind of friend**).
'left' becomes 'l' (common abbreviation).
'in front of' says to put letters next to each other.
'soldiers' becomes 'or' (Other Rank).
'pal'+'l'+'or'='PALLOR'
'from' is the link.
(Other definitions for pallor that I've seen before include "Lack of facial colour as from illness" , "Unhealthy whiteness" , "Bloodlessness" , "Whiteness of face as from illness" , "Ashen complexion due to illness" .)