Bad opening to summer, distressing after father leaves (6)

I believe the answer is:

sinful

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

'bad' is the definition.
(I've seen this before)

I can't explain the remainder of the clue.

(Other definitions for sinful that I've seen before include "Habitually wicked" , "Morally wrong; wicked" , "Offensive to God" , "Wicked, unholy" , "Bad" .)

I've seen this clue in The Independent.

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