### Clue: Swelling muscles two seconds back (7)
### Answer: ABSCESS 
 ### Explanation: Definition: Swelling
 ABS(short for the abdominal muscles) + **reversal of**(… back) [ S(abbrev. for "second", in time notation) + SEC(short for the time period of a second, the second of two seconds in this clue) ].
Defn: … or inflammation leading to pus accumulation.