Think about giving welcome to good man (6)
I believe the answer is:
knight
'think' is the definition.
Although both the answer and definition are singular nouns, I can't see how one could define the other.
'about giving welcome to good man' is the wordplay.
'about' shows that the letters should be reversed in order.
'giving' becomes 'thin' (I can't justify this - if you can you should give a lot more credence to this answer).
'welcome' indicates putting letters inside (in sense of 'inviting in').
'to good' becomes 'g' (abbreviation).
'man' becomes 'k' (abbreviation for king, a chess man).
'thin' going around 'g' is 'thgin'.
'thgin'+'k'='thgink'
'thgink' back-to-front is 'KNIGHT'.
Can you help me to learn more?
(Other definitions for knight that I've seen before include "Gawain?" , "Give title to; chess piece" , "He's a Sir in the UK" , "horse in game!" , "Chess piece shaped like hors's head" .)