Male is upset with son lacking in purpose (7)

I believe the answer is:

aimless

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'lacking in purpose' is the definition.
'aimless' can be an answer for 'purpose' (I have seen 'Lacking purpose' mean 'aimless' so perhaps 'purpose' could also mean 'aimless'). I am unsure of the 'lacking in' bit.

'male is upset with son' is the wordplay.
'upset' indicates anagramming the letters.
'with' is a charade indicator (letters next to each other).
'son' becomes 's' ().
'male'+'is'='maleis'
'maleis' with letters rearranged gives 'aimles'.
'aimles'+'s'='AIMLESS'

Can you help me to learn more?

(Other definitions for aimless that I've seen before include "Haphazard" , "Like characters in 5D {WAITING FOR GODOT]" , "Drifting - Melissa (anag)" , "at a loose end" , "not knowing where to go?" .)

I've seen this clue in The Times.

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