A crack angler, it is said (7)
I believe the answer is:
fissure
'a crack' is the definition.
('fissure' can be a synonym of 'crack')
'angler it is said' is the wordplay.
'angler' becomes 'fisher' (I've seen this before).
'it is said' indicates a 'sounds like' (homophone) clue.
'fisher' sounds like 'FISSURE'.
(Other definitions for fissure that I've seen before include "Cleft" , "Deep crack in rock" , "Long, narrow crack" , "Split, crack" , "Long, narrow opening" .)