### Clue: Mock self-contained man with dyke, thin on top (5,2)
### Answer: SCOFF AT 
 ### Explanation: Definition: Mock
  SC(*self-contained*, as used in SCUBA,sc underwater breathing apparatus, or in accommodation advertisements to indicate that an apartment has got full facilities within) + OFFA(8C Anglo-Saxon king who built a *dyke* between his kingdom and what is now Wales) + T(first letter,*top* of *thin*, I think).