In military base help to guard one grounded (7)
I believe the answer is:
airhead
'in military base help to guard one grounded' is the definition.
I can't judge whether this definition defines the answer.
'in military base help to guard one' is the wordplay.
'in' means one lot of letters goes inside another.
'military' becomes 'aread' (I can't justify this - if you can you should believe this answer much more).
'base' suggests taking the first letters (I've seen 'base of' mean this).
'to guard' means one lot of letters goes inside another.
'one' becomes 'i' (Roman numeral).
The initial letter of 'help' is 'h'.
'aread' enclosing 'h' is 'arhead'.
'arhead' placed around 'i' is 'AIRHEAD'.
(Other definitions for airhead that I've seen before include "Featherbrain" , "clown" , "One's simple" , "Someone with nothing between the ears?" , "Dope" .)