Cavalryman about, in country road on right (6)
I believe the answer is:
lancer
'cavalryman' is the definition.
(lancer is a kind of cavalryman)
'about in country road on right' is the wordplay.
'about' becomes 'c' (abbreviation for 'circa'**).
'in' means one lot of letters goes inside another.
'country road' becomes 'lane' (I've seen this before).
'on' means one lot of letters go next to another.
'right' becomes 'r' (common abbreviation).
'c' going within 'lane' is 'lance'.
'lance'+'r'='LANCER'
(Other definitions for lancer that I've seen before include "Former cavalryman" , "Spearman (as in dance?)" , "Cavalry soldier" .)