Line over river blocked by points failure (5)
I believe the answer is:
loser
'failure' is the definition.
(someone who has failed)
'line over river blocked by points' is the wordplay.
'line over' becomes 'lo' (this might be a standard abbreviation which I don't know about).
'river' becomes 'r' (abbreviation for river).
'blocked by' indicates putting letters inside (I've seen this in other clues).
'points' becomes 'se'.
'lo'+'r'='lor'
'lor' enclosing 'se' is 'LOSER'.
Can you help me to learn more?
(Other definitions for loser that I've seen before include "One who is always a failure" , "Winner's opponent" , "One not winning" , "Person who's a failure" , "sad type?" .)