Found in prison, a dire low point (5)
I believe the answer is:
nadir
'low point' is the definition.
(I've seen this before)
'found in prison a dire' is the wordplay.
'found in' says the answer is hidden in the clue.
'NADIR' can be found hidden inside 'prison a dire'.
(Other definitions for nadir that I've seen before include "Lower one cannot get!" , "least successful point" , "pits" , "businessman formerly escaping justice" , "Low point" .)