Answer: fissure

AnswerCrossword Clue
FISSURENarrow opening
FISSURERift
FISSUREOrgan groove
FISSURENarrow gap
FISSURECrack
FISSURECleft in a rock.
FISSURESplit.
FISSURENarrow opening.
FISSURECleft
FISSURELava comes out of it
FISSURELong, narrow crack
FISSURECleavage
FISSURECerebral groove
fissurenarrow opening
fissureto split (to separate lengthwise)