Dic: part (as an uncountable noun)

3. QUANT : QUANT of sing-n OR n-uncount △Part of something is some of it.

• It was a very severe accident and he lost part of his foot.
• Mum and he were able to walk part of the way together.

7. N-SING : poss N in n △Your part in something that happens is your involvement in it.

• If only he could conceal his part in the accident. (= involvement)

..... Cobuild

1. SOME | [uncountable]part of something △some but not all of a thing.

• We spent part of the time in the museum.
• Part of the building was destroyed in the fire.
• Voters are given only part of the story (= only some of the information).
• Part of me feels sorry for him (= I feel partly, but not entirely, sorry for him).

3. MEMBER | [uncountable] △a member of something; a person or thing that, together with others, makes up a single unit.

• You need to be able to work as part of a team.

...... OALD

CF. 8. N-UNCOUNT : also a N, N of n △If something or someone is part of a group or organization, they belong to it or are included in it.

• I was a part of the team and wanted to remain a part of the team.

.... Cobuild