In speech ex-PM beguiles table (6)
I believe the answer is:
matrix
'table' is the definition.
(mathematical table)
'in speech ex' is the wordplay.
'in speech' becomes 'matri' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'ex' becomes 'x'.
'matri'+'x'='MATRIX'
'pm beguiles' is the link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
(Other definitions for matrix that I've seen before include "Grid-like array of rat mix" , "Mathematical array; The --, sci-fi film" , "network of circuit elements" , "Arrangement of numbers" , "Casting mould" .)