Base for soldier rising to titled rank (7)
I believe the answer is:
ignoble
'base' is the definition.
(both can mean dishonourable or shameful)
'soldier rising to titled rank' is the wordplay.
'soldier' becomes 'GI' (term for US soldier).
'rising' is a reversal indicator (in a down clue, letters go up).
'to titled rank' becomes 'noble' (I can't justify this - if you can you should believe this answer much more).
'gi' reversed gives 'ig'.
'ig'+'noble'='IGNOBLE'
'for' acts as a link.
Can you help me to learn more?
(Other definitions for ignoble that I've seen before include "not in the top class" , "'Far from the madding crowd's . . . . . . . strife'" , "Debased in character or purpose" , "Not honourable, low" , "Lacking dignity" .)