Cooking a fish, performing in style (7)
I believe the answer is:
fashion
'style' is the definition.
(I know that fashion is a type of style)
'cooking a fish performing' is the wordplay.
'cooking' indicates anagramming the letters (letters cooked up into a new form).
'performing' becomes 'on' (as in being on stage).
'a'+'fish'='afish'
'afish' is an anagram of 'fashi'.
'fashi'+'on'='FASHION'
'in' is the link.
(Other definitions for fashion that I've seen before include "way" , "Vogue, trend" , "Make; popular trend" , "Vogue, style" , "Trend, mode" .)