Whirlwind is to trouble, sucking in Royal Navy (7)
I believe the answer is:
tornado
'whirlwind' is the definition.
(I know that whirlwind can be written as tornado)
'to trouble sucking in royal navy' is the wordplay.
'trouble' becomes 'ado' (both can mean bother or commotion).
'sucking in' is an insertion indicator.
'royal navy' becomes 'RN' (abbreviation for Royal Navy).
'to'+'ado'='toado'
'toado' enclosing 'rn' is 'TORNADO'.
'is' is the link.
(Other definitions for tornado that I've seen before include "great deal of wind" , "Dreadful blow" , "wind-up" , "squall" , "Violent twister" .)