Field position makes member err (3,4)
I believe the answer is:
leg slip
'field position' is the definition.
I don't know anything about this answer so I cannot judge whether it can be defined by this definition.
'member err' is the wordplay.
'member' becomes 'leg' (member can mean a limb).
'err' becomes 'slip' (synonyms).
'leg'+'slip'='LEG SLIP'
'makes' acts as a link.
Can you help me to learn more?
(Other definitions for leg slip that I've seen before include "One hoping to hold ball" , "One in the field" , "Cricketer" , "Position on cricket field" , "that may be found in field" .)