According to plan, got rent reviewed around middle of May (2,6)
I believe the answer is:
on target
'according to plan' is the definition.
'got rent reviewed around middle of may' is the subsidiary indication.
'reviewed' indicates anagramming the letters (To look at again and re view).
'around' means one lot of letters goes inside another.
'middle of' says to take the centre.
The middle letters of 'may' are 'a'.
'got'+'rent'='gotrent'
'gotrent' anagrammed gives 'ontrget'.
'ontrget' enclosing 'a' is 'ontarget'.
(Other definitions for on target that I've seen before include "Up to the planned level" , "Keeping to a course" , "Where bull may be" , "Reaching the aim point" , "Accurate (shot)" .)