Shy fellow seen during party, extremely uncool (7)
I believe the answer is:
bashful
'shy' is the definition.
(I've seen this before)
'fellow seen during party extremely uncool' is the wordplay.
'fellow' becomes 'F' (abbreviation - of a society etc.).
'seen during' indicates putting letters inside.
'party' becomes 'bash' (term for a party or celebration).
'extremely' says to hollow out the word (remove centre letters) (only the extremes of the word are used).
'uncool' with its middle taken out is 'ul'.
'bash'+'ul'='bashul'
'f' going into 'bashul' is 'BASHFUL'.
(Other definitions for bashful that I've seen before include "Shy and self-conscious" , "reserved" , "Shy, easily embarrassed" , "Sleepy companion" , "Shovel and pick worker" .)