Some fissure turned up as a source of life (6)
I believe the answer is:
uterus
'a source of life' is the definition.
'some fissure turned up' is the wordplay.
'some' indicates the answer is hidden within the clue (some of the parts of the word are used).
'up' shows that the letters should be reversed in order (in down clue: letters go upwards).
'suretu' is hidden in the letters of 'fissure turned'.
'suretu' reversed gives 'UTERUS'.
'as' acts as a link.
(Other definitions for uterus that I've seen before include "development centre" , "Latin name for the womb" , "The formal womb" , "Here, conceive" , "Organ" .)