The most common and most likely answer to this crossword clue is the 12 letter word STREAMLINING
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More clues leading to the result STREAMLINING
Buddy explains!

The straight part
We know that "Eliminating excess" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case eliminating excess = streamlining.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.
What does STREAMLINING mean?
STREAMLINING verb- To design and construct the contours of a vehicle etc. so as to offer the least resistance to its flow through a fluid.
- (by extension) To simplify or organize a process in order to increase its efficiency.
- To modernise.
- The process by which something is streamlined.