Rest start to do all right (5)
I believe the answer is:
dwell
'rest' is the definition.
(thesaurus)
'start to do all right' is the wordplay.
'start to' suggests taking the first letters.
'all right' becomes 'well' ('well' can be a synonym of 'all right').
The initial letter of 'do' is 'd'.
'd'+'well'='DWELL'
(Other definitions for dwell that I've seen before include "Live (in a place)" , "Exist (within)" , "stay" , "Focus attention (on)" , "Settle" .)