Cheerful camp greeting may conceal aching heart (2-2-2)

I believe the answer is:

hi-de-hi

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

'cheerful camp greeting' is the definition.
I know nothing about this answer so I can't judge whether it can be defined by this definition.

'conceal aching heart' is the wordplay.
'conceal' becomes 'hide' (synonyms).
'heart' indicates the central letters.
The middle letters of 'aching' are 'hi'.
'hide'+'hi'='HI-DE-HI'

'may' is the link.

Can you help me to learn more?

I've seen this clue in The Irish Times.

Want a hint initially instead of a full solution? Install my app