Fresh sage under coating of asparagus — one spear (7)
I believe the answer is:
assegai
'spear' is the definition.
(I know that assegai is a type of spear)
'fresh sage under coating of asparagus one' is the wordplay.
'fresh' indicates anagramming the letters.
'under' is a charade indicator (letters next to each other).
'coating of' suggests removing the centre (only the letters that coat the word remain).
'one' becomes 'I' (Roman numeral).
'asparagus' with its centre removed is 'as'.
'sage' with letters rearranged gives 'sega'.
'sega' put after 'as' is 'assega'.
'assega'+'i'='ASSEGAI'
(Other definitions for assegai that I've seen before include "A Zulu warrior's spear" , "Wooden spear of southern Africa" , "African weapon" , "Zulu fighting spear" , "Spear used in southern Africa" .)