One proposing exercise to iron man (9)
I believe the answer is:
nominator
'one proposing exercise' is the definition.
The definition suggests a singular noun which matches the answer.
'to iron man' is the wordplay.
'to iron man' anagrams to 'NOMINATOR'.
However, I am not sure how this is indicated.
Can you help me to learn more?
(Other definitions for nominator that I've seen before include "One who puts forward a candidate for election" , "One proposing candidate" , "One who proposes" , "The proposer" , "someone who makes proposal" .)