Tip given by Harold, playwright trapping ball (7)
I believe the answer is:
pointer
'tip given by harold' is the definition.
'pointer' can be an answer for 'tip' (I've seen this in another clue). I'm unsure of the 'given by harold' bit.
'playwright trapping ball' is the wordplay.
'playwright' becomes 'pinter' (Harold Pinter).
'trapping' means one lot of letters goes inside another.
'ball' becomes 'o' (O looks like a ball).
'pinter' going around 'o' is 'POINTER'.
Can you help me to learn more?
(Other definitions for pointer that I've seen before include "stick used for instruction?" , "Dog < or horse or" , "Arrow" , "under control of mouse" , "Guide" .)