Long sentence in biography (4)
I believe the answer is:
life
I believe this clue is a double definition.
'long sentence' is the first definition.
(life in prison)
'biography' is the second definition.
(synonyms)
'in' acts as a link.
(Other definitions for life that I've seen before include "Existence - biography" , ""But an empty dream" (Longfellow) - "As tedious as a twice-told tale" (Shakespeare)" , "'While there's .... there's hope'" , "Baffin oiler (anag) - 7 film" , "Maximum stretch?" .)