Sign a concern, briefly pointing the wrong way (5)
I believe the answer is:
arrow
'sign' is the definition.
(I know that arrow is a symbols)
'a concern briefly pointing the wrong way' is the wordplay.
'concern' becomes 'worry' (synonyms).
'briefly' means to remove the last letter.
'pointing the wrong way' says the letters should be written backwards.
'worry' with its last letter taken away is 'worr'.
'worr' in reverse letter order is 'rrow'.
'a'+'rrow'='ARROW'
(Other definitions for arrow that I've seen before include "The bowman's missile" , "Something pointing" , "Direction symbol" , "pointer to the way forward" , "Sharp-tipped missile" .)