Head of course again in position on cricket field (5)
I believe the answer is:
cover
'position on cricket field' is the definition.
'head of course again' is the wordplay.
'head of' indicates taking the first letters.
'again' becomes 'over' (as in the phrases 'start over' and 'start again').
The initial letter of 'course' is 'c'.
'c'+'over'='COVER'
'in' acts as a link.
(Other definitions for cover that I've seen before include "Sit on - suffice for" , "Mask, hide" , "(Put) lid (on) - fielding position - insurance" , "Encompass" , "Overlay" .)