Stop on the way (4)
I believe the answer is:
'stop' is the definition.
(to take a rest is to stop)
'on the way' is the wordplay.
'on' becomes 're' ('on' can be mean 'with reference to').
'the way' becomes 'st' (abbreviation for street).
(Other definitions for rest that I've seen before include "Surplus" , "Change is as good as this, they say" , "'Relax, pause from work (4)'" , "Leisure" , "Pole in Crucible?" .)