Tropical fish in Trent area, oddly (5)
I believe the answer is:
tetra
'tropical fish' is the definition.
(I've seen this in another clue)
'trent area oddly' is the wordplay.
'oddly' indicates alternate letters (letters in odd-numbered positions).
'trent'+'area'='trentarea'
The alternating letters of 'trentarea' are 'TETRA'.
'in' acts as a link.
(Other definitions for tetra that I've seen before include "With four parts" , "Swimmer" , "Wrongful act (Law)" , "Brightly coloured aquarium fish" , "Bright tropical fish" .)