Sampling first of these nuts in yogurt (6,3)
I believe the answer is:
trying out
'sampling' is the definition.
('try out' can be a synonym of 'sample')
'first of these nuts in yogurt' is the wordplay.
'first of' says to take the initial letters.
'nuts' indicates anagramming the letters (nuts can mean crazy).
The first letter of 'these' is 't'.
'in'+'yogurt'='inyogurt'
'inyogurt' with letters rearranged gives 'ryingout'.
't'+'ryingout'='TRYING OUT'
(Other definitions for trying out that I've seen before include "sampling" , "Experimenting with" .)