Block inexperienced reporter heading east (4)
I believe the answer is:
cube
'block' is the definition.
('cube' can be a synonym of 'block')
'inexperienced reporter heading east' is the wordplay.
'inexperienced reporter' becomes 'cub' (I've seen this in other clues).
'heading east' becomes 'e' (abbreviation).
'cub'+'e'='CUBE'
(Other definitions for cube that I've seen before include "Regular hexahedron" , "Product of three equal numbers" , "nine?" , "Square-faced solid" , "Three dimetional shape" .)