Travel around eastern Maine to test some maths (8)
I believe the answer is:
geometry
'some maths' is the definition.
(geometry is a kind of maths)
'travel around eastern maine to test' is the wordplay.
'travel' becomes 'go' ('go' can be a synonym of 'travel'**).
'around' indicates putting letters inside.
'eastern' becomes 'e'.
'maine' becomes 'me'.
'to test' becomes 'try' ('try' can be a synonym of 'test').
'go' going around 'e' is 'geo'.
'geo'+'me'+'try'='GEOMETRY'
(Other definitions for geometry that I've seen before include "Mathematical study of points, lines, curves, surfaces etc" , "Branch of mathematics" , "Maths dealing with lines, angles etc - Euclid was good at it" , "Field of pure mathematics" , "Branch of maths associated with Euclid" .)