Crop head of state out of good shot (4)
I believe the answer is:
snip
'crop' is the definition.
('snip' can be a synonym of 'crop')
'head of state out of good shot' is the wordplay.
'head of state' becomes 'er' (abbreviation for Elizabeth Regina).
'out of' is a deletion indicator.
'good shot' becomes 'sniper' (I've seen this before).
'sniper' with 'er' taken out is 'SNIP'.
(Other definitions for snip that I've seen before include "Cut back" , "Cut quickly with a scissors" , "Cut using pins" , "Cut with scissors - bargain" , "Trim, clip" .)