So in love, Ryan (4)
I believe the answer is:
very
'so' is the definition.
(I've seen this in another clue)
'in love ryan' is the wordplay.
'in' says the answer is hidden in the clue.
'VERY' is hidden in the letters of 'love ryan'.
(Other definitions for very that I've seen before include "Kind of light" , "Exceedingly" , "light, perhaps" , "Sort of light" , "Ever so" .)