The most common and most likely answer to this crossword clue is the 7 letter word FAWNING
F
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W
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Buddy explains!

The straight part
We know that "subservient" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case subservient = fawning.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 FAWNING mean?
FAWNING verb- To give birth to a fawn.
- To exhibit affection or attempt to please.
- To seek favour by flattery and obsequious behaviour (with on or upon).
- (of a dog) To show devotion or submissiveness by wagging its tail, nuzzling, licking, etc.
- Servile flattery.
- Seeking favor by way of flattery; flattering, servile.