Extent of odds studied (6)
I believe the answer is:
spread
'extent' is the definition.
(thesaurus)
'odds studied' is the wordplay.
'odds' becomes 'sp' (betting abbreviation for starting price).
'studied' becomes 'read' (I've seen this before).
'sp'+'read'='SPREAD'
'of' is the link.
(Other definitions for spread that I've seen before include "Scatter or distribute more thinly" , "American farm" , "Apply thinly" , "Stretch out; big meal" , "butter?" .)