Closed up cell, finally having eased suspect outside (6)
I believe the answer is:
sealed
'closed' is the definition.
(sealing is a kind of closing)
'having eased suspect outside' is the wordplay.
'having' becomes 'l' (I am not sure about this - if you are sure you should believe this answer much more).
'suspect' indicates anagramming the letters (a suspicious or unusual spelling).
'outside' means one lot of letters goes inside another (some letters go outside others).
'eased' is an anagram of 'seaed'.
'l' put into 'seaed' is 'SEALED'.
'up cell finally' acts as a link.
This may not be correct. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for sealed that I've seen before include "Stamped as authentic" , "Shut up tight" , "Leased in secured state" , "Securely fastened" , "Closed (of lips, envelope, tomb etc)" .)