The most common and most likely answer to this crossword clue is the 5 plus 3 letter word EAGLE EYE
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More clues leading to the result EAGLE EYE
- An achievement, of course — yes, picked up a good looker
- Old solvers following each singsong have excellent sight
- Sweetheart’s a joy — short but a really good looker
- Critical inspection of comic featuring Dan Dare and investigator
- English agree to swap sides, yet mostly will display great acuity
- In each part-song you find keenness of observation
- What helps one to observe closely? Detective goes after no big dog
- Top dog, say I, for close observation
Buddy explains!

The straight part
We know that "What helps one to observe closely?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case what helps one to observe closely? = eagle eye.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.