Call otolaryngology department, having gaping lips (7)

I believe the answer is:

ringent

I'm a little stuck... Click here to teach me more about this clue!

'gaping lips' is the definition.
'ringent' can be an answer for 'gaping' (thesaurus). I'm not sure about the 'lips' bit.

'call otolaryngology department' is the wordplay.
'call' becomes 'ring' (telephone call).
'otolaryngology department' becomes 'ent' (I am not sure about this - if you are sure you should believe this answer much more).
'ring'+'ent'='RINGENT'

'having' acts as a link.

Can you help me to learn more?

(Another definition for ringent that I've seen is " wide open".)

I've seen this clue in The Independent.

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