Number taking part in strange trial by entrance to Hampton maze (9)
I believe the answer is:
labyrinth
'maze' is the definition.
(I know that maze can be written as labyrinth)
'number taking part in strange trial by entrance to hampton' is the wordplay.
'number' becomes 'n' (n can represent any number).
'taking part in' indicates putting letters inside.
'strange' indicates an anagram.
'entrance to' says to take the initial letters.
The initial letter of 'hampton' is 'h'.
'trial'+'by'+'h'='trialbyh'
'trialbyh' is an anagram of 'labyrith'.
'n' going inside 'labyrith' is 'LABYRINTH'.
(Other definitions for labyrinth that I've seen before include "Complex network of passages" , "It may be difficult to get out of" , "Maze, tangled network" , "puzzle -" , "Passages in cutting" .)