Hit song's opening part dragged (7)

I believe the answer is:

slugged

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'part dragged' is the definition.
The definition and answer can be both to do with contact as well as being past participle verbs.
Maybe they are linked in a way I don't understand?

'hit song's opening' is the wordplay.
'hit' becomes 'slug' (slugging is a kind of hitting).
'song's opening' becomes 'ged' (I am not sure about this - if you are sure you should believe this answer much more).
'slug'+'ged'='SLUGGED'

Can you help me to learn more?

(Another definition for slugged that I've seen is " Given heavy blow".)

I've seen this clue in The Daily Express.

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