Old stone tools making Leo this upset? (7)
I believe the answer is:
eoliths
'old stone tools' is the definition.
(I've seen this in another clue)
'making leo this upset?' is the wordplay.
'making' indicates anagramming the letters.
'upset?' indicates anagramming the letters (I've seen 'upsets' mean this).
'leo' is an anagram of 'eol'.
'this' anagrammed gives 'iths'.
'eol'+'iths'='EOLITHS'
(Other definitions for eoliths that I've seen before include "Rocks" , "bits of stone" , "Roughly chipped flints; hostile (anag.)" , "Early stone implements" , "Pieces of flint" .)