Study by unit head is being prepared (9)
I believe the answer is:
readiness
'being prepared' is the definition.
(I've seen this before)
'study by unit head' is the wordplay.
'study' becomes 'read' ('read' can be a synonym of 'study').
'by unit' becomes 'i' ('I' can be a synonym of 'unit'. I am not sure about the 'by' bit.**).
'head' becomes 'ness' (ness is a headland).
'read'+'i'+'ness'='READINESS'
'is' is the link.
(Other definitions for readiness that I've seen before include "State of preparedness" , "Inclination" , "Promptitude" , "Immediate availability" , "State of being prepared and willing" .)