Going according to plan that's unfortunately not great (2,6)
I believe the answer is:
on target
'going according to plan' is the definition.
(I've seen this in another clue)
'unfortunately not great' is the wordplay.
'unfortunately' indicates anagramming the letters (a bad or unfortunate spelling).
'not'+'great'='notgreat'
'notgreat' is an anagram of 'ON TARGET'.
'that's' is the link.
(Other definitions for on target that I've seen before include "Accurate (shot)" , "Keeping to a course" , "Heading in the right direction" , "Where bull may be" , "Reaching the aim point" .)