Top dog, say I, for close observation (5,3)
I believe the answer is:
eagle eye
'top dog' is the definition.
Both the answer and definition are singular nouns.
Maybe you can see an association between them that I can't see?
'say i for close observation' is the wordplay.
'say' shows a homophone (sound like).
'for' means one lot of letters go next to another (I've seen this in other clues).
'close observation' becomes 'eagle' (I am not sure about this - if you are sure you should believe this answer much more).
'i' is a homophone of 'eye'.
'eye' after 'eagle' is 'EAGLE-EYE'.
Can you help me to learn more?
(Other definitions for eagle eye that I've seen before include "Keen sight" , "Ability to observe fine detail" , "Critical inspection" , "one envisages a long way off" , "Keenness of vision" .)