I've unfortunately been overwhelmed by a yearning to succeed (7)
I believe the answer is:
achieve
'succeed' is the definition.
(achieving is a kind of succeeding)
'i've unfortunately been overwhelmed by' is the wordplay.
'unfortunately' indicates an anagram (a bad or unfortunate spelling).
'been' becomes 'ache' (I can't justify this - if you can you should give a lot more credence to this answer).
'overwhelmed by' is an insertion indicator (inserted letters get absorbed or overwhelmed).
'ive' with letters rearranged gives 'iev'.
'iev' inserted inside 'ache' is 'ACHIEVE'.
'a yearning to' is the link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for achieve that I've seen before include "Reach; be successful" , "Skilfully bring about" , "Have ice (anag.)" , "Successfully bring off" , "Effect" .)