Determined soldier standing behind a barrier (7)
I believe the answer is:
adamant
'determined' is the definition.
(I've seen this in another clue)
'standing behind a barrier' is the wordplay.
'standing' becomes 'ant' (I can't justify this - if you can you should give a lot more credence to this answer).
'behind' means one lot of letters go next to another.
'barrier' becomes 'dam' (dam is a kind of barrier).
'a'+'dam'='adam'
'ant' put after 'adam' is 'ADAMANT'.
'soldier' acts as a link.
Can you help me to learn more?
(Other definitions for adamant that I've seen before include "Imaginary rock" , "Firm and unyielding" , "Refusing to change opinion" , "Obdurate and unyielding" , "Inexorable" .)