(verb) play mud and sand; Or (figurative meaning) someone is like playing kid games and never get serious
Definitions (粵典–words.hk)
動詞
細路仔玩嘅嘢，引申指做嘢唔認真、兒戲、唔專業，好似細路仔玩噉 literally to play with mud and sand; figuratively, to do something in a childish manner, unprofessionally