Extent of displeasure right at the start (5)
I believe the answer is:
range
'extent' is the definition.
(I know that range is a type of extent)
'displeasure right at the start' is the wordplay.
'displeasure' becomes 'ange' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'right' becomes 'r' (common abbreviation).
'at the start' says to put letters next to each other.
'ange' after 'r' is 'RANGE'.
'of' is the link.
Can you help me to learn more?
(Other definitions for range that I've seen before include "Extent - shooting area" , "Take sides" , "Large, grassy land for livestock in the US" , "Cattle country - mountains - scope - stove" , "Area of variation" .)