Terrorising first worker with strange outburst (7)
I believe the answer is:
tantrum
'outburst' is the definition.
(I've seen this before)
'terrorising first worker with strange' is the wordplay.
'terrorising first' becomes 't' (1st letter of 'terrorising').
'worker' becomes 'ant' (worker is a type of ant).
'with' means one lot of letters go next to another.
'strange' becomes 'rum' (similar in meaning).
't'+'ant'+'rum'='TANTRUM'
(Other definitions for tantrum that I've seen before include "Childish angry outburst" , "Fit of ill-temper" , "Frenzy" , "Burst of rage" , "Display of bad temper" .)