Like the water at the pierhead? (4)
I believe the answer is:
deep
'like' is the definition.
Both the definition and answer are adjectives. Perhaps you can see an association between them that I don't see?
'water at the pierhead?' is the wordplay.
'water' becomes 'dee' (I can't explain this - if you can you should believe this answer much more).
'at' is a charade indicator (letters next to each other).
'the pierhead?' becomes 'p' (head letter of 'pier').
'dee'+'p'='DEEP'
'the' is the link.
Can you help me to learn more?
(Other definitions for deep that I've seen before include "Intense -- extreme" , "Wise - difficult to understand" , "hard to understand" , "Profound - engrossed" , "hard to follow" .)