It's wide and curved, with substantial height (5)
I believe the answer is:
bight
'it's wide and curved' is the definition.
I can't judge whether this definition defines the answer.
'with substantial height' is the wordplay.
'with' is a charade indicator (letters next to each other).
'substantial' becomes 'big' (I've seen this in another clue).
'height' becomes 'ht' (abbreviation).
'big' put next to 'ht' is 'BIGHT'.
Can you help me to learn more?
(Other definitions for bight that I've seen before include "Wide bay" , "Coastline curve forming a bay" , "Bay, sounds like a morsel of food" , "Large broad bay -- middle part of a slack rope" , "Curve of shore" .)