Beat time, leading to odd childish outburst (7)
I believe the answer is:
tantrum
'childish outburst' is the definition.
(I've seen this before)
'beat time leading to odd' is the wordplay.
'beat' becomes 'tan' (I've seen this before**).
'time' becomes 't'.
'leading to' is a charade indicator (letters next to each other) (some letters go before or lead others).
'odd' becomes 'rum' (I've seen this before).
'tan'+'t'+'rum'='TANTRUM'
(Other definitions for tantrum that I've seen before include "Childish fit of rage" , "Uncontrolled outburst of anger" , "Childish fit of anger" , "Childish display of temper" , "Hissy fit" .)