Second summit attended by those spearheading economic research and Sir Lindsay Hoyle, perhaps (7)
I believe the answer is:
speaker
'spearheading economic research and sir lindsay hoyle perhaps' is the definition.
I can't judge whether this definition defines the answer.
'second summit attended by those' is the wordplay.
'second' becomes 's' (common abbreviation).
'summit' becomes 'peak' (mountain peak).
'attended by' means one lot of letters go next to another.
'those' becomes 'er' (I can't explain this - if you can you should give a lot more credence to this answer).
's'+'peak'+'er'='SPEAKER'
Can you help me to learn more?
(Other definitions for speaker that I've seen before include "Officer of House of Commons" , "He asks for order" , "one who restores order" , "Person presiding over British House of Commons or similar assembly" , "Commons presiding officer" .)