Comrade covers for fellow in gaol (6)
I believe the answer is:
remand
'gaol' is the definition.
(synonyms)
'comrade covers for fellow in' is the wordplay.
'comrade' becomes 'roland' (I have seen 'Comrade of Oliver ' mean 'roland' so perhaps 'comrade' could also mean 'roland').
'covers' means to remove the middle letters (I've seen 'covering' mean this (the letters which cover the word are used)).
'for fellow' becomes 'eman' (I can't explain this - if you can you should give a lot more credence to this answer).
'in' means one lot of letters goes inside another.
'roland' with its middle removed is 'rd'.
'rd' placed around 'eman' is 'REMAND'.
Can you help me to learn more?
(Other definitions for remand that I've seen before include "Keep in custody while waiting for trial" , "Place of detention for young offenders" , "Send back, into custody say" , "Put a defendant on bail or in custody" , "Return (often) to custody" .)