Case of sunstroke initially stopping nice tan developing (8)
I believe the answer is:
instance
'case' is the definition.
(synonyms)
'sunstroke initially stopping nice tan developing' is the wordplay.
'initially' says to take the initial letters.
'stopping' indicates putting letters inside (stopping can mean blocking a gap).
'developing' indicates an anagram.
The first letter of 'sunstroke' is 's'.
'nice'+'tan'='nicetan'
'nicetan' anagrammed gives 'intance'.
's' placed into 'intance' is 'INSTANCE'.
'of' acts as a link.
(Other definitions for instance that I've seen before include "'Example, illustration (8)'" , "Specimen" , "Cite as an example" , "Exemplify" , "Particular example" .)