They suspend the second grade competitions (6)
I believe the answer is:
braces
'they suspend' is the definition.
The definition suggests an adverb but the answer is not.
'second grade competitions' is the wordplay.
'second grade' becomes 'b' (I can't justify this - if you can you should give a lot more credence to this answer).
'competitions' becomes 'races' (race is a kind of competition).
'b'+'races'='BRACES'
'the' is the link.
Can you help me to learn more?
(Other definitions for braces that I've seen before include "Appliances to correct dental irregularities" , "Support for trousers" , "Supports for teeth or trousers" , "bolsters" , "Tighten" .)