Tramp's son developed into cricketer (9)
I believe the answer is:
sportsman
'cricketer' is the definition.
(thesaurus)
'tramp's son developed' is the wordplay.
'developed' indicates anagramming the letters.
'tramps'+'son'='trampsson'
'trampsson' anagrammed gives 'SPORTSMAN'.
'into' acts as a link.
(Other definitions for sportsman that I've seen before include "Chap aiming for game" , "Game fellow" , "player" , "Eg, athlete" , "He engages in physical games" .)