Wears out sleepers around river (5)
I believe the answer is:
tires
'wears' is the definition.
('tire' can be a synonym of 'wear')
'out sleepers around river' is the wordplay.
'out' means one lot of letters goes inside another.
'sleepers' becomes 'ties' ('tie' can be a synonym of 'sleeper').
'around river' becomes 'r' (abbreviation. I am not sure about the 'around' bit.).
'ties' placed around 'r' is 'TIRES'.
Can you help me to learn more?
(Other definitions for tires that I've seen before include "Wearies" , "Weakens" , "Grows weary of rites" , "Becomes weary and in need of rest" , "Exhausts" .)