Staggeringly closely? (7)
I believe the answer is:
tightly
'staggeringly' is the definition.
Both the definition and answer are adverbs. Perhaps there's a link between them I don't understand?
'closely?' is the wordplay.
I cannot quite see how this works, but
'closely?' could be 'tight' ('tight' can be a synonym of 'closely') and 'tight' is located in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for tightly that I've seen before include "In a close-fitting manner" , "Securely" .)