Completely OTT about pieces in plot (9)
I believe the answer is:
allotment
'plot' is the definition.
(thesaurus)
'completely ott about pieces in' is the wordplay.
'completely' becomes 'all' ('all' can be a synonym of 'completely').
'about pieces' becomes 'men' ('man' can be a synonym of 'piece'. I am not sure about the 'about' bit.**).
'in' is an insertion indicator.
'ott' going around 'men' is 'otment'.
'all'+'otment'='ALLOTMENT'
Can you help me to learn more?
(Other definitions for allotment that I've seen before include "Share - small piece of land rented for cultivation" , "Small rented gardening plot" , "share in growing concern?" , "growing area?" , "Allowance" .)