HQ not so much without foundation (8)
I believe the answer is:
baseless
'without foundation' is the definition.
('foundation' can be 'base' (synonyms) so maybe 'without foundation' can be ''baseless')
'hq not so much' is the wordplay.
'hq' becomes 'base' (HQ is headquarters).
'not so much' becomes 'less' (I've seen this in another clue).
'base'+'less'='BASELESS'
(Other definitions for baseless that I've seen before include "Without foundation, unjustified" , "With no foundation in fact" , "Groundless, unfounded" , "like a bed with just a mattress?" , "Lacking foundation, as rumours may" .)