For demonstration (not real SE questions):
"How do you pilot a hovercraft?"
is a subset of
"How do you drive a vehicle?"
Supposing the answers to the second question contain no mention of hovercrafts, but do contain some very broad principles that may be technically useful, but which are practically not very useful, would the first question a duplicate of the second?
If the answer is yes, and the answers to the original question are very weak with regard to applicability to the subset, is there anything the asker can do? My guess is to start a bounty (and give a description of the goal in the bounty). But that could have a downside in tainting the original (general) question with too much discussion about the specifics of the narrowly focussed question.