Basic resetting of ankle limits boxer (8)
I believe the answer is:
alkaline
'basic' is the definition.
(similar in meaning)
'resetting of ankle limits boxer' is the wordplay.
'resetting of' indicates anagramming the letters (I've seen 'reset' mean this).
'limits' indicates putting letters inside (limit can mean to contain or block off).
'boxer' becomes 'Ali' (Muhammad Ali).
'ankle' is an anagram of 'alkne'.
'alkne' going around 'ali' is 'ALKALINE'.
(Other definitions for alkaline that I've seen before include "To do with substances neutralized by acids" , "Having a pH greater than seven" , "caustic?" , "Basic" , "base, perhaps" .)