I say, look closely at the structure built into the water (4)
I believe the answer is:
pier
'the water' is the definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Maybe there's an association between them I don't understand?
'i say look closely at the structure built' is the wordplay.
I cannot quite see how this works, but
'i' is found in the answer.
The remaining letters 'per' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
'into' acts as a link.
Can you help me to learn more?
(Other definitions for pier that I've seen before include "Seaside platform" , "Structure with a deck, built over water" , "Load-bearing pillar" , "Ripe as a jetty (4)" , "Buttress; landing place" .)