Aimless raid ruined fort (6)
I believe the answer is:
adrift
'aimless' is the definition.
(synonyms)
'raid ruined fort' is the wordplay.
'ruined' indicates anagramming the letters.
'fort' becomes 'ft' (abbreviation in place names).
'raid' with letters rearranged gives 'adri'.
'adri'+'ft'='ADRIFT'
(Other definitions for adrift that I've seen before include "Unanchored at sea" , "without purpose or direction" , "Off course" , "No longer fixed in position" , "out of touch" .)