Aims tennis shot, getting round one in a hundred (10)
I believe the answer is:
intentions
'aims' is the definition.
('intention' can be a synonym of 'aim')
'tennis shot getting round one in a hundred' is the wordplay.
'shot' indicates anagramming the letters.
'getting round' indicates putting letters inside.
'one' becomes 'I' (Roman numeral).
'in' indicates putting letters inside.
'a hundred' becomes 'ton' (I've seen this before).
'tennis' anagrammed gives 'intens'.
'i' put inside 'ton' is 'tion'.
'intens' enclosing 'tion' is 'INTENTIONS'.
(Other definitions for intentions that I've seen before include "Aims" , "The goal with respect to a marriage proposal?" .)