Basic alert with enemy on the move (10)
I believe the answer is:
elementary
'basic' is the definition.
('elementary' can be similar in meaning to 'basic')
'alert with enemy on the move' is the wordplay.
'with' is a charade indicator (letters next to each other).
'on the move' indicates anagramming the letters.
'alert'+'enemy'='alertenemy'
'alertenemy' with letters rearranged gives 'ELEMENTARY'.
(Other definitions for elementary that I've seen before include "Primary" , "No problem" , "One precursor to 7 [SECONDARY MODERN]" , "Simple, my dear Watson!" , "description of subatomic particle" .)