Elite basketballers need ball for hit-up (5)
I believe the answer is:
opals
'elite basketballers need' is the definition.
I can't tell whether this definition defines the answer.
'ball for hit-up' is the wordplay.
'ball' becomes 'o' (O looks like a ball).
'for' means one lot of letters go next to another.
'hit' becomes 'slap' (both can mean to strike).
'up' shows that the letters should be reversed in order (in down clue: letters go upwards).
'slap' reversed gives 'pals'.
'o'+'pals'='OPALS'
Can you help me to learn more?
(Other definitions for opals that I've seen before include "Translucent gemstones" , "Milky-white stones" , "jewellery" , "Milky gemstones with delicate colours" , "Semi-precious stones of milky or bluish colour" .)