Officer harms Henry (7)
I believe the answer is:
marshal
'officer' is the definition.
(I've seen this before)
'harms henry' is the wordplay.
'harms' becomes 'mars'.
'henry' becomes 'hal'.
'mars'+'hal'='MARSHAL'
(Other definitions for marshal that I've seen before include "Usher" , "Assemble and arrange" , "Top officer" , "US federal officer" , "US law officer" .)