Sentence structure (6,4)
There are a few possibilities for this:
prison cell
'sentence structure?' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for prison that I've seen before include "No rips (anag)" , "Place of incarceration" , "Place of detention for criminals" , "punishment" , "Clink - jug" .)
'sentence structure' is the definition.
(synonyms)
This is the entire clue.
(Other definitions for syntax that I've seen before include "Grammatical rules" , "Rules governing formation of words into sentences etc" , "Grammatical word structure in sentences" , "Grammatical construction" , "The rules governing the arranging of words" .)
(Another definition for prison cell that I've seen is " place of convicts".)