Moan about CID backing wandering (7)
I believe the answer is:
nomadic
'wandering' is the definition.
(I know that wandering can be written as nomadic)
'moan about cid backing' is the wordplay.
'about' is an anagram indicator.
'backing' shows that the letters should be reversed in order.
'cid' in reverse letter order is 'dic'.
'moan' anagrammed gives 'noma'.
'noma'+'dic'='NOMADIC'
(Other definitions for nomadic that I've seen before include "Unsettled" , "always moving?" , "Homeless - wandering" , "Perhaps unsettling" , "Roaming" .)