Clue: Wilful child mostly climbing, say, around home (9)
Answer: OBSTINATE
Explanation: Definition: Wilful
 **Reversal of**(… climbing, in a down clue) "boy"(child) **minus ****its last letter**(mostly) + STATE(to say/to declare) ] **containing**(around) IN(at home, as in "I'm home if you want to visit").