Two-star result in the least favourable circumstances (2,5)
I believe the answer is:
at worst
'in the least favourable circumstances' is the definition.
I can't judge whether this definition defines the answer.
'two-star result' is the wordplay.
'result' indicates anagramming the letters (I've seen 'result of' mean this).
'two'+'star'='twostar'
'twostar' is an anagram of 'AT WORST'.
Can you help me to learn more?
(Other definitions for at worst that I've seen before include "most pessimistically" , "In the most negative circumstances" , "Taking the most pessimistic view" , "in the most serious state" , "Taking blackest view" .)