Deepen a waterway delta and river bank? (6)
I believe the answer is:
dredge
'deepen a waterway' is the definition.
(I've seen this before)
'delta and river bank?' is the wordplay.
'delta' becomes 'd' (phonetic alphabet: alpha, bravo, charlie etc.).
'and' means one lot of letters go next to another.
'river' becomes 'r' (abbreviation for river).
'bank?' becomes 'edge' (bank can mean the edge or side of something).
'd'+'r'+'edge'='DREDGE'
(Other definitions for dredge that I've seen before include "Sort of collector" , "Clean mud as from silted harbour" , "Clean out river/harbour" , "Dig up mud from river or canal bed" , "Remove mud from a riverbed" .)