Limits to using lavatory? Nasty (4)

I believe the answer is:

ugly

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'nasty' is the definition.
(thesaurus)

'limits to using lavatory?' is the wordplay.
'limits to' means to remove the middle letters (only the edge letters are used).
'lavatory?' becomes 'ly' (I can't explain this - if you can you should believe this answer much more).
'using' with its centre taken out is 'ug'.
'ug'+'ly'='UGLY'

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(Other definitions for ugly that I've seen before include "Far from beautiful" , "Not easy on the eye" , "Disquieting" , "Visually unpleasant; dangerous (situation)" , "Offensive to one's sight or other senses" .)

I've seen this clue in The Times.

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