Oscar stood up in predicament, showing great bottle (8)
I believe the answer is:
jeroboam
'great bottle' is the definition.
'jeroboam' can be an answer for 'bottle' (jeroboam is a kind of bottle). I am not sure about the 'great' bit.
'oscar stood up in predicament' is the wordplay.
'oscar' becomes 'O' (phonetic alphabet: alpha, bravo, charlie etc.).
'stood' becomes 'bore' (I've seen this in another clue).
'up' is a reversal indicator (in down clue: letters go upwards).
'in' indicates putting letters inside.
'predicament' becomes 'jam' (jam can mean a tricky situation).
'o'+'bore'='obore'
'obore' back-to-front is 'erobo'.
'erobo' placed inside 'jam' is 'JEROBOAM'.
'showing' is the link.
Can you help me to learn more?
(Other definitions for jeroboam that I've seen before include "large sparkling container?" , "Very large wine bottle named after Israeli king" , "Wine bottle 4-12 times the ordinary size" , "a lot of bottle?" , "'Large wine bottle, equal to four standard ones (8)'" .)