Wherein to field for a number of overs (6)
I believe the answer is:
covers
'wherein to field' is the definition.
I can't judge whether this defines the answer.
'number of overs' is the wordplay.
'number of' becomes 'c' (I can't justify this - if you can you should give a lot more credence to this answer).
'c'+'overs'='COVERS'
'for a' acts as a link.
Can you help me to learn more?
(Other definitions for covers that I've seen before include "Bedclothes" , "Forms a layer over" .)