Curse as no room squeezing into big top? (7)
I believe the answer is:
torment
'curse' is the definition.
(synonyms)
'no room squeezing into big top?' is the wordplay.
'no' becomes 'o' (resembles 0 - 'no' can mean 'zero').
'room' becomes 'rm' (I've seen this in other clues).
'squeezing into' indicates putting letters inside.
'big top?' becomes 'tent' (big top is a kind of tent).
'o'+'rm'='orm'
'orm' inserted within 'tent' is 'TORMENT'.
'as' acts as a link.
(Other definitions for torment that I've seen before include "Pester annoyingly" , "Cause great pain to" , "Torture" , "Extreme mental or physical distress" , "Agony of mind" .)