A UK force returns from a long distance (4)
I believe the answer is:
afar
'from a long distance' is the definition.
(I've seen this in another clue)
'a uk force returns' is the wordplay.
'uk force' becomes 'raf' (I am not sure about this - if you are sure you should believe this answer much more).
'returns' says the letters should be written backwards.
'raf' reversed gives 'far'.
'a'+'far'='AFAR'
Can you help me to learn more?
(Other definitions for afar that I've seen before include "Distant, not near" , "Distant parts" , "Many a mile" , "quite some distance" , "Not in this neighbourhood" .)