More secure but less sober (7)

I believe the answer is:

tighter

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'more secure' is the definition.
('tight' can be similar in meaning to 'secure')

I can't explain the remainder of the clue.

Can you help me to learn more?

(Other definitions for tighter that I've seen before include "More constricted" , "more closely" , "Less loose" , "even more tense" , "More close-fitting" .)

I've seen this clue in The Daily Express.

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