The most common and most likely answer to this crossword clue is the 3 plus 3 plus 4 plus 4 letter word FOR THE MOST PART
I've seen this crossword clue in The Times
F
O
R
T
H
E
M
O
S
T
P
A
R
T
More clues leading to the result FOR THE MOST PART
- First pair of thespians engaged in leading role, mainly
- Mainly leading role around Thursday
- River top, stream beaten usually
- Hatters top — form exceptional, mainly
- At present, initiate is taking in piano chiefly
- Team sport organised alongside river, generally
- Jumping to and fro to keep trim, begin to gain power generally
Buddy explains!
The straight part
We know that "Mainly" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case mainly = for the most part.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.