Penny and Heather admitting Daisy is laying it on a bit thick, perhaps (10)

'laying it on a bit thick perhaps' is the definition.
I can't tell whether this definition defines the answer.

'penny and heather admitting daisy' is the wordplay.
'penny' becomes 'p' (short for pence).
'and' says to put letters next to each other.
'heather' becomes 'ling' (synonyms).
'admitting' is an insertion indicator (admit can mean to welcome in or accept).
'daisy' becomes 'aster' (I've seen this before).
'ling' placed around 'aster' is 'lastering'.
'p'+'lastering'='PLASTERING'

'is' acts as a link.

Can you help me to learn more?