Return an act of respect for a man of substance (5)
I believe the answer is:
nabob
'a man of substance' is the definition.
(thesaurus)
'return an act of respect' is the wordplay.
'return' shows that the letters should be reversed in order.
'act of respect' becomes 'bob' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'an' backwards is 'na'.
'na'+'bob'='NABOB'
'for' acts as a link.
Can you help me to learn more?
(Other definitions for nabob that I've seen before include "Wealthy influential person" , "One divining (water)" , "Mogul governor; rich man" , "Wealthy and powerful person" , "Person of great wealth" .)