Outlaw keeping old brother in line (3,3)
I believe the answer is:
rob roy
'outlaw' is the definition.
Although both the answer and definition are singular nouns, I cannot see how they can define each other.
'old brother in line' is the wordplay.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'brother' becomes 'bro' (short for brother).
'in' is an insertion indicator.
'line' becomes 'ry' (abbreviation for railway).
'o'+'bro'='obro'
'obro' put within 'ry' is 'ROB ROY'.
'keeping' is the link.
Can you help me to learn more?
(Other definitions for rob roy that I've seen before include "Famous 17th century bandit of Scottish highlands" , "Persistently trouble" , "Scottish outlaw and folk hero, d. 1734" , "Scots hero" , "Scottish outlaw, subject of a Sir Walter Scott novel" .)