Sleepers run in rows (5)
I believe the answer is:
tiers
'rows' is the definition.
(tier is a kind of row)
'sleepers run in' is the wordplay.
'sleepers' becomes 'ties' ('tie' can be a synonym of 'sleeper').
'run' becomes 'r' (cricket abbreviation).
'in' means one lot of letters goes inside another.
'ties' placed around 'r' is 'TIERS'.
(Other definitions for tiers that I've seen before include "Tries (anag.)" , "Layers of rites" , "Rows; ranks" , "Row upon row" , "aprons for kids" .)