Stop retired military man entering storage unit (5)
I believe the answer is:
block
'stop' is the definition.
(synonyms)
'retired military man entering storage unit' is the wordplay.
I cannot quite understand how this works, but
'man' could be 'lock' and 'lock' is found within the answer.
'unit' could be 'b' (B is an example) and 'b' is present in the answer.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for block that I've seen before include "Solid lump" , "Impede, prevent" , "Jam" , "Mass of wood etc - set of buildings" , "building development" .)