Gas about formerly getting openings for Rolling Thunder gigs (8)
I believe the answer is:
concerts
'rolling thunder gigs' is the definition.
'concerts' can be an answer for 'gigs' (musical concerts). I'm not sure about the 'rolling thunder' bit.
'gas about formerly getting openings' is the wordplay.
'gas' becomes 'CS' (short for t-chlorobenzalmalononitrile).
'about' indicates putting letters inside.
'formerly' becomes 'once' (synonyms).
'getting openings' becomes 'rt' (I am not sure about this - if you are sure you should believe this answer much more).
'once'+'rt'='oncert'
'cs' placed around 'oncert' is 'CONCERTS'.
'for' acts as a link.
(Other definitions for concerts that I've seen before include "Performances of music" , "shows" , "Public musical performances" .)