The most common and most likely answer to this crossword clue is the 14 letter word WHOLEHEARTEDLY
I've seen this crossword clue in The Sunday Telegraph
W
H
O
L
E
H
E
A
R
T
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D
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Y
More clues leading to the result WHOLEHEARTEDLY
Buddy explains!

The straight part
We know that "With total effort" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case with total effort = wholeheartedly.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 WHOLEHEARTEDLY mean?
WHOLEHEARTEDLY adverb- In a wholehearted manner; enthusiastically; without reserve.