They're a comfort to those retiring in deep trouble taking courage on top of stoicism (3-5,7)

'they're a comfort to those retiring' is the definition.
The definition suggests an adverb but the answer is not.

'deep trouble taking courage on top of stoicism' is the wordplay.
'deep trouble' becomes 'hot water' (I've seen this in another clue).
'taking' is a charade indicator (letters next to each other).
'courage' becomes 'bottle' (bottle can mean courage).
'on top of' says to take the initial letters.
The first letter of 'stoicism' is 's'.
'hotwater'+'bottle'+'s'='HOT-WATER BOTTLES'

'in' is the link.

Can you help me to learn more?