Clue: Mob wants me to go off in a while, having retreated? (4,4)
Answer: TIME BOMB
Explanation: Mob wants me to go off in a while, having retreated? (4,4)
An envelope ('in') of MEBOM, an anagram ('to go off') of 'mob' plus 'me' in TIB, a reversal ('having retreated') of BIT ('while' "I'll get round to it in a bit"), with an extended definition, if not a very accurate one.