Solution is containing virus at the start of spiral! (5)
I believe the answer is:
curve
'spiral' is the definition.
(thesaurus)
'solution is containing virus at the start' is the wordplay.
'solution' becomes 'cure'.
'is containing' is an insertion indicator.
'at the start' says to take the initial letters.
The first letter of 'virus' is 'v'.
'cure' placed around 'v' is 'CURVE'.
'of' acts as a link.
(Other definitions for curve that I've seen before include "Comparable in some respects" , "No part of this line is straight" , "that may be hyperbolic" , "Not the straightforward" , "Gentle bend, arc" .)