I caught bird that's pulled up lettuce (7)
I believe the answer is:
iceberg
'lettuce' is the definition.
(I know that iceberg is a type of lettuce)
'i caught bird that's pulled up' is the wordplay.
'caught' becomes 'c' (cricket abbreviation).
'bird' becomes 'grebe' (type of bird).
'that's pulled up' shows that the letters should be reversed in order.
'grebe' reversed gives 'eberg'.
'i'+'c'+'eberg'='ICEBERG'
(Other definitions for iceberg that I've seen before include "Arctic shipping hazard" , "smash hit in Titanic?" , "Mass calved from a glacier" , "Largely hidden danger" , "Polar shipping hazard" .)