Structure at the pierhead only? (5)
I believe the answer is:
pylon
'structure' is the definition.
(pylon is a kind of structure)
'at the pierhead only?' is the wordplay.
I cannot really understand how this works, but
'at' could be 'on' (location) and 'on' is present in the answer.
'pierhead' could be 'p' (head letter of 'pier') and 'p' is found within the answer.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for pylon that I've seen before include "Tall cable carrier" , "Bearer of cable" , "Electricity grid construction" , "Steel tower supporting high-tension wires" , "Power cables supporter" .)