Pastry Lee Mack shortly demolished, bit by bit (9)
I believe the answer is:
piecemeal
'bit by bit' is the definition.
(synonyms)
'pastry lee mack shortly demolished' is the wordplay.
'pastry' becomes 'pie' (pie is a kind of pastry).
'shortly' means to remove the last letter.
'demolished' indicates an anagram.
'lee'+'mack'='leemack'
'leemack' with its last letter taken away is 'leemac'.
'leemac' with letters rearranged gives 'cemeal'.
'pie'+'cemeal'='PIECEMEAL'
(Other definitions for piecemeal that I've seen before include "A bit at a time" , "Claim epee in gradual unsystematic way" , "by degrees" , "Bit by bit; unsystematic" , "a little at a time" .)