Tense worker, with odd display of temper (7)
I believe the answer is:
tantrum
'display of temper' is the definition.
(temper tantrum)
'tense worker with odd' is the wordplay.
'tense' becomes 't' (grammatical abbreviation).
'worker' becomes 'ant' (worker is a type of ant).
'with' says to put letters next to each other.
'odd' becomes 'rum' (rum can mean strange or dubious).
't'+'ant'+'rum'='TANTRUM'
(Other definitions for tantrum that I've seen before include "Childish fit of rage" , "Pet, temper" , "Fit of ill-temper" , "Childish display of temper" , "Child's outburst of bad temper" .)