Wasted litre on friend, precisely (9)
I believe the answer is:
literally
'precisely' is the definition.
(I've seen this before)
'wasted litre on friend' is the wordplay.
'wasted' indicates anagramming the letters.
'on' says to put letters next to each other.
'friend' becomes 'ally' (an ally is a friend or supporter).
'litre' with letters rearranged gives 'liter'.
'liter'+'ally'='LITERALLY'
(Other definitions for literally that I've seen before include "Without exaggeration" , "Exactly as stated" , "Absolutely" , "Not figuratively" , "precisely as written" .)