Homesickness leaving Poles nagging pain (7)

I believe the answer is:

otalgia

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'nagging pain' is the definition.
'otalgia' can be an answer for 'pain' (otalgia is a kind of pain). I'm not certain of the 'nagging' bit.

'homesickness leaving poles' is the wordplay.
'homesickness' becomes 'nostalgia' (I've seen this before).
'leaving' suggests deleting specific letters.
'poles' becomes 'SN' (North and South poles).
'nostalgia' with 'sn' removed is 'OTALGIA'.

Can you help me to learn more?

(Other definitions for otalgia that I've seen before include "Ear ache" , "painful condition" , "Earache" , "pain!" , "Problem with ears" .)

I've seen this clue in The Telegraph.

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