Was able to start up in frosty conditions (5)
I believe the answer is:
could
'was able to' is the definition.
(I've seen this before)
'start up in frosty conditions' is the wordplay.
'start' means to remove the last letter (I've seen 'starts' mean this).
'in' indicates putting letters inside.
'frosty conditions' becomes 'cold' (I am not sure about this - if you are sure you should believe this answer much more).
'up' with its last letter taken off is 'u'.
'u' placed inside 'cold' is 'COULD'.
Can you help me to learn more?
(Another definition for could that I've seen is " Was able to (do something)".)