Highest ball missed opener in cricket match (7)
I believe the answer is:
tallest
'highest' is the definition.
('tall' can be similar in meaning to 'high')
'opener in cricket match' is the wordplay.
'opener' becomes 'all' (I am not sure about this - if you are sure you should believe this answer much more).
'in' indicates putting letters inside.
'cricket match' becomes 'test' (a test is a kind of cricket match).
'all' placed within 'test' is 'TALLEST'.
'ball missed' is the link.
This may not be right. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for tallest that I've seen before include "Most high" , "Of greatest vertical extent" , "highest standing" , "Of greatest height" , "Top out" .)