Go and tread unwarily around the pierhead (6)
I believe the answer is:
depart
'go' is the definition.
(synonyms)
'tread unwarily around the pierhead' is the wordplay.
I cannot really see how this works, but
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is found in the answer.
'pierhead' could be 'p' (head letter of 'pier') and 'p' is found within the answer.
The remaining letters 'dear' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
'and' is the link.
Can you help me to learn more?
(Other definitions for depart that I've seen before include "Prated (anag.)" , "Retire from" , "Make an exit" , "Leave (6)" , "Quit" .)