More trying to set out some mathematics (12)
I believe the answer is:
trigonometry
'some mathematics' is the definition.
(trigonometry is a kind of mathematics)
'more trying to set out' is the wordplay.
'set out' indicates an anagram.
'more'+'trying'+'to'='moretryingto'
'moretryingto' anagrammed gives 'TRIGONOMETRY'.
(Other definitions for trigonometry that I've seen before include "Mathematics of the relationship between angles and sides of triangles" , "mathematical skill" , "Branch of maths" , "degree-level study" , "Branch of mathematics" .)