Maybe being a goal ahead can mean calm waters (6)
I believe the answer is:
lagoon
'maybe being a' is the definition.
I can't tell whether this definition defines the answer.
'goal ahead can mean calm waters' is the wordplay.
I cannot quite see how this works, but
an anagram of 'goal' is 'lago' which is within the answer.
'ahead' could be 'on' (synonyms) and 'on' is located in the answer.
This accounts for all the letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for lagoon that I've seen before include "A slat-water lake" , "Shallow salt-water lake" , "Atoll's enclosed water" , "A salt-water lake in the sea" , "Salt-water lake, often blue" .)