Destructive wave in N Uist swirling round before noon (7)
I believe the answer is:
tsunami
'destructive wave' is the definition.
(I've seen this before)
'n uist swirling round before noon' is the wordplay.
'swirling' indicates an anagram.
'round' indicates putting letters inside.
'before noon' becomes 'am'.
'n'+'uist'='nuist'
'nuist' with letters rearranged gives 'tsuni'.
'tsuni' placed around 'am' is 'TSUNAMI'.
'in' acts as a link.
(Other definitions for tsunami that I've seen before include "Seismic sea wave" , "Large tidal wave" , "Strong surge" , "I am nuts! (anag)" , "Huge wave caused by earth tremor" .)