Irregular pressure: expression of surprise in danger (9)
I believe the answer is:
haphazard
'irregular' is the definition.
(thesaurus)
'pressure expression of surprise in danger' is the wordplay.
'pressure' becomes 'p' (abbreviation).
'expression of surprise' becomes 'ha'.
'in' indicates putting letters inside.
'danger' becomes 'hazard' (hazard is a kind of danger**).
'p'+'ha'='pha'
'pha' going inside 'hazard' is 'HAPHAZARD'.
(Other definitions for haphazard that I've seen before include "Careless or random" , "Lacking any obvious organisation" , "Disorganised, random" , "Slapdash, slipshod" , "Lacking order" .)