Perhaps older person might become exhausted in Irish lake (7)
I believe the answer is:
retiree
'perhaps older person' is the definition.
'retiree' can be an answer for 'person' (retiree is a kind of person). I am not certain of the 'perhaps older' bit.
'become exhausted in irish lake' is the wordplay.
'become exhausted' becomes 'tire' (I've seen this in another clue).
'in' is an insertion indicator.
'irish lake' becomes 'ree' (I can't explain this - if you can you should give a lot more credence to this answer).
'tire' inserted into 'ree' is 'RETIREE'.
'might' acts as a link.
Can you help me to learn more?
(Other definitions for retiree that I've seen before include "One ceasing to work" , "Pensioner" , "One having completed work" , "One who has ceased to work" , "Person out of work" .)