Weak bowling technique Cook sees, getting over 50 (9)
I believe the answer is:
spineless
'weak' is the definition.
(similar in meaning)
'bowling technique cook sees getting over 50' is the wordplay.
'bowling technique' becomes 'spin' (cricket).
'cook' is an anagram indicator.
'getting over' is an insertion indicator.
'50' becomes 'l' (Roman numeral).
'sees' is an anagram of 'eess'.
'eess' enclosing 'l' is 'eless'.
'spin'+'eless'='SPINELESS'
(Other definitions for spineless that I've seen before include "Cowardly, lacking backbone" , "Craven, lacking vertebrae" , "Yellow" , "Weak, without purpose" , "Not like Mrs Tiggy-Winkle" .)