1
general::
Phrase(s): have a finger in the pie [and] have one’s finger in the pie
Fig. to have a role in something; to be involved in something. (See also have one’s finger in too many pies) • Tess wants to have a finger in the pie. She doesn’t think we can do it by ourselves. • Sally always wants to have a finger in the pie.
McGrawhill's American Idioms And Phrasal Verbs
2
general::
Have an interest in or meddle in something. For example, When they nominated me for the board, I'm sure Bill had a finger in the pie. Another form of this idiom is have a finger in every pie, meaning "to have an interest in or be involved in everything," as in She does a great deal for the town; she has a finger in every pie. The precise origin of this metaphor, which presumably alludes either to tasting every pie or being involved in their concoction, has been lost. [Late 1500s]
American Heritage Idioms