Call up troops, two officers besieging City (9)
I believe the answer is:
recollect
'call up' is the definition.
(thesaurus)
'troops two officers besieging city' is the wordplay.
I cannot really see how this works, but
'troops' could be 're' (I've seen this in other clues) and 're' is found in the answer.
'city' could be 'ec' (the City of London postcode) and 'ec' is found in the answer.
This may be the basis of clue (or it may be nonsense).
(Other definitions for recollect that I've seen before include "Remember" , "Reminisce" , "Look back on" , "Call to mind" , "Bring back to mind." .)