Worried ram tails one crying 'wolf!' (8)
I believe the answer is:
alarmist
'one crying wolf' is the definition.
(I've seen this before)
'worried ram tails' is the wordplay.
'worried' indicates an anagram.
'ram'+'tails'='ramtails'
'ramtails' with letters rearranged gives 'ALARMIST'.
(Other definitions for alarmist that I've seen before include "Creating needless worry" , "(Person) creating unnecessary panic" , "Like panicking passenger" , "Calamity Jane" , "Given to causing unnecessary panic" .)