Chancy thing to do in a tube train (3)
I believe the answer is:
bet
'chancy thing to do' is the definition.
I can't judge whether this defines the answer.
'in a tube train' is the wordplay.
'in' indicates a hidden word.
'BET' is hidden in the letters of 'tube train'.
Can you help me to learn more?
(Other definitions for bet that I've seen before include "Wager, back" , "Money risked on a gamble" , "Speculation" , "'Stake, wager (3)'" , "Wager, speculate" .)