Lizards disturbed us again (7)
I believe the answer is:
iguanas
'lizards' is the definition.
(iguana is a kind of lizard)
'disturbed us again' is the wordplay.
'disturbed' is an anagram indicator.
'us'+'again'='usagain'
'usagain' is an anagram of 'IGUANAS'.
(Other definitions for iguanas that I've seen before include "American arboreal lizards" , "tropical natives" , "Monitors" , "Large lizards" , "Asia gun (anag.)" .)