All perfect praise be to Allah, the Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad is His slave and Messenger.
Fear that is without legitimate justification and which is based on mere illusions and obsessive whispers or on weakness and cowardice does not justify for one to pray the prayer of fear or to combine the prayers that can be combined.
As regards the fear that is justified, then it is permissible for the scared person to pray the prayer of fear, but he should not delay the prayer after its time. He should do the acts of the prayer that he is able to do and nod with his head for the bowing or prostration, and he is exempted from the conditions of the prayer that he is unable to fulfill.
Kash-shaaf Al-Qinaa’ reads:
"…if he fears for himself, his family, or his money/property if he performed the prayer as it should be performed (with its conditions and pillars), then due to extreme fear he may pray the prayer of extreme fear, as this is included in the general meaning of the verse (which means): {And if you fear [an enemy], then [pray] on foot or riding…} [Quran 2:239]; or if he needs to defend himself or his family or his money/property or to defend someone else's life, then he may pray the prayer of fear in order to ward off the transgressor from himself, his family, or his money or from another person."
Allah knows best.