Ultimate feature of tennis court? (3)
I believe the answer is:
net
This clue is a double definition.
'ultimate' is the first definition.
('net' can be similar in meaning to 'ultimate')
'feature of tennis court?' is the second definition.
(Other definitions for net that I've seen before include "Capture" , "It turns in every direction" , "Trap; open-weave fabric" , "What separates court opponents" , "Open-meshed material (used for catching things?)" .)